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PERLAPI(1)                                 Perl Programmers Reference Guide                                PERLAPI(1)



NAME
       perlapi - autogenerated documentation for the perl public API

DESCRIPTION
       This file contains the documentation of the perl public API generated by embed.pl, specifically a listing of
       functions, macros, flags, and variables that may be used by extension writers.  At the end is a list of
       functions which have yet to be documented.  The interfaces of those are subject to change without notice.  Any
       functions not listed here are not part of the public API, and should not be used by extension writers at all.
       For these reasons, blindly using functions listed in proto.h is to be avoided when writing extensions.

       Note that all Perl API global variables must be referenced with the "PL_" prefix.  Some macros are provided
       for compatibility with the older, unadorned names, but this support may be disabled in a future release.

       Perl was originally written to handle US-ASCII only (that is characters whose ordinal numbers are in the range
       0 - 127).  And documentation and comments may still use the term ASCII, when sometimes in fact the entire
       range from 0 - 255 is meant.

       Note that Perl can be compiled and run under EBCDIC (See perlebcdic) or ASCII.  Most of the documentation (and
       even comments in the code) ignore the EBCDIC possibility.  For almost all purposes the differences are
       transparent.  As an example, under EBCDIC, instead of UTF-8, UTF-EBCDIC is used to encode Unicode strings, and
       so whenever this documentation refers to "utf8" (and variants of that name, including in function names), it
       also (essentially transparently) means "UTF-EBCDIC".  But the ordinals of characters differ between ASCII,
       EBCDIC, and the UTF- encodings, and a string encoded in UTF-EBCDIC may occupy more bytes than in UTF-8.

       Also, on some EBCDIC machines, functions that are documented as operating on US-ASCII (or Basic Latin in
       Unicode terminology) may in fact operate on all 256 characters in the EBCDIC range, not just the subset
       corresponding to US-ASCII.

       The listing below is alphabetical, case insensitive.

"Gimme" Values
       GIMME   A backward-compatible version of "GIMME_V" which can only return "G_SCALAR" or "G_ARRAY"; in a void
               context, it returns "G_SCALAR".  Deprecated.  Use "GIMME_V" instead.

                       U32     GIMME

       GIMME_V The XSUB-writer's equivalent to Perl's "wantarray".  Returns "G_VOID", "G_SCALAR" or "G_ARRAY" for
               void, scalar or list context, respectively. See perlcall for a usage example.

                       U32     GIMME_V

       G_ARRAY Used to indicate list context.  See "GIMME_V", "GIMME" and perlcall.

       G_DISCARD
               Indicates that arguments returned from a callback should be discarded.  See perlcall.

       G_EVAL  Used to force a Perl "eval" wrapper around a callback.  See perlcall.

       G_NOARGS
               Indicates that no arguments are being sent to a callback.  See perlcall.

       G_SCALAR
               Used to indicate scalar context.  See "GIMME_V", "GIMME", and perlcall.

       G_VOID  Used to indicate void context.  See "GIMME_V" and perlcall.


       av_create_and_push
               Push an SV onto the end of the array, creating the array if necessary.  A small internal helper
               function to remove a commonly duplicated idiom.

               NOTE: this function is experimental and may change or be removed without notice.

                       void    av_create_and_push(AV **const avp,
                                                  SV *const val)

       av_create_and_unshift_one
               Unshifts an SV onto the beginning of the array, creating the array if necessary.  A small internal
               helper function to remove a commonly duplicated idiom.

               NOTE: this function is experimental and may change or be removed without notice.

                       SV**    av_create_and_unshift_one(AV **const avp,
                                                         SV *const val)

       av_delete
               Deletes the element indexed by "key" from the array, makes the element mortal, and returns it.  If
               "flags" equals "G_DISCARD", the element is freed and null is returned.  Perl equivalent: "my $elem =
               delete($myarray[$idx]);" for the non-"G_DISCARD" version and a void-context "delete($myarray[$idx]);"
               for the "G_DISCARD" version.

                       SV*     av_delete(AV *av, I32 key, I32 flags)

       av_exists
               Returns true if the element indexed by "key" has been initialized.

               This relies on the fact that uninitialized array elements are set to &PL_sv_undef.

               Perl equivalent: "exists($myarray[$key])".

                       bool    av_exists(AV *av, I32 key)

       av_extend
               Pre-extend an array.  The "key" is the index to which the array should be extended.

                       void    av_extend(AV *av, I32 key)

       av_fetch
               Returns the SV at the specified index in the array.  The "key" is the index.  If lval is true, you are
               guaranteed to get a real SV back (in case it wasn't real before), which you can then modify.  Check
               that the return value is non-null before dereferencing it to a "SV*".

               See "Understanding the Magic of Tied Hashes and Arrays" in perlguts for more information on how to use
               this function on tied arrays.

               The rough perl equivalent is $myarray[$idx].

                       SV**    av_fetch(AV *av, I32 key, I32 lval)

       av_fill Set the highest index in the array to the given number, equivalent to Perl's "$#array = $fill;".

                       I32     av_len(AV *av)

       av_make Creates a new AV and populates it with a list of SVs.  The SVs are copied into the array, so they may
               be freed after the call to av_make.  The new AV will have a reference count of 1.

               Perl equivalent: "my @new_array = ($scalar1, $scalar2, $scalar3...);"

                       AV*     av_make(I32 size, SV **strp)

       av_pop  Pops an SV off the end of the array.  Returns &PL_sv_undef if the array is empty.

               Perl equivalent: "pop(@myarray);"

                       SV*     av_pop(AV *av)

       av_push Pushes an SV onto the end of the array.  The array will grow automatically to accommodate the
               addition.  This takes ownership of one reference count.

               Perl equivalent: "push @myarray, $elem;".

                       void    av_push(AV *av, SV *val)

       av_shift
               Shifts an SV off the beginning of the array.  Returns &PL_sv_undef if the array is empty.

               Perl equivalent: "shift(@myarray);"

                       SV*     av_shift(AV *av)

       av_store
               Stores an SV in an array.  The array index is specified as "key".  The return value will be NULL if
               the operation failed or if the value did not need to be actually stored within the array (as in the
               case of tied arrays). Otherwise, it can be dereferenced to get the "SV*" that was stored there (=
               "val")).

               Note that the caller is responsible for suitably incrementing the reference count of "val" before the
               call, and decrementing it if the function returned NULL.

               Approximate Perl equivalent: "$myarray[$key] = $val;".

               See "Understanding the Magic of Tied Hashes and Arrays" in perlguts for more information on how to use
               this function on tied arrays.

                       SV**    av_store(AV *av, I32 key, SV *val)

       av_undef
               Undefines the array.  Frees the memory used by the av to store its list of scalars.  If any
               destructors are triggered as a result, the av itself may be freed.

                       void    av_undef(AV *av)

       av_unshift
               Unshift the given number of "undef" values onto the beginning of the array.  The array will grow
               automatically to accommodate the addition.  You must then use "av_store" to assign values to these new

               NOTE: the perl_ form of this function is deprecated.

                       AV*     get_av(const char *name, I32 flags)

       newAV   Creates a new AV.  The reference count is set to 1.

               Perl equivalent: "my @array;".

                       AV*     newAV()

       sortsv  Sort an array. Here is an example:

                   sortsv(AvARRAY(av), av_len(av)+1, Perl_sv_cmp_locale);

               Currently this always uses mergesort. See sortsv_flags for a more flexible routine.

                       void    sortsv(SV** array, size_t num_elts,
                                      SVCOMPARE_t cmp)

       sortsv_flags
               Sort an array, with various options.

                       void    sortsv_flags(SV** array, size_t num_elts,
                                            SVCOMPARE_t cmp, U32 flags)

Callback Functions
       call_argv
               Performs a callback to the specified named and package-scoped Perl subroutine with "argv" (a NULL-
               terminated array of strings) as arguments. See perlcall.

               Approximate Perl equivalent: "&{"$sub_name"}(@$argv)".

               NOTE: the perl_ form of this function is deprecated.

                       I32     call_argv(const char* sub_name, I32 flags,
                                         char** argv)

       call_method
               Performs a callback to the specified Perl method.  The blessed object must be on the stack.  See
               perlcall.

               NOTE: the perl_ form of this function is deprecated.

                       I32     call_method(const char* methname, I32 flags)

       call_pv Performs a callback to the specified Perl sub.  See perlcall.

               NOTE: the perl_ form of this function is deprecated.

                       I32     call_pv(const char* sub_name, I32 flags)

       call_sv Performs a callback to the Perl sub whose name is in the SV.  See perlcall.


                       SV*     eval_pv(const char* p, I32 croak_on_error)

       eval_sv Tells Perl to "eval" the string in the SV. It supports the same flags as "call_sv", with the obvious
               exception of G_EVAL. See perlcall.

               NOTE: the perl_ form of this function is deprecated.

                       I32     eval_sv(SV* sv, I32 flags)

       FREETMPS
               Closing bracket for temporaries on a callback.  See "SAVETMPS" and perlcall.

                               FREETMPS;

       LEAVE   Closing bracket on a callback.  See "ENTER" and perlcall.

                               LEAVE;

       SAVETMPS
               Opening bracket for temporaries on a callback.  See "FREETMPS" and perlcall.

                               SAVETMPS;

Character case changing
       toLOWER Converts the specified character to lowercase in the platform's native character set, if possible;
               otherwise returns the input character itself.

                       char    toLOWER(char ch)

       toUPPER Converts the specified character to uppercase in the platform's native character set, if possible;
               otherwise returns the input character itself.

                       char    toUPPER(char ch)

Character classes
       There are three variants for all the functions in this section.  The base ones operate using the character set
       of the platform Perl is running on.  The ones with an "_A" suffix operate on the ASCII character set, and the
       ones with an "_L1" suffix operate on the full Latin1 character set.  All are unaffected by locale and by "use
       bytes".

       For ASCII platforms, the base function with no suffix and the one with the "_A" suffix are identical.  The
       function with the "_L1" suffix imposes the Latin-1 character set onto the platform.  That is, the code points
       that are ASCII are unaffected, since ASCII is a subset of Latin-1.  But the non-ASCII code points are treated
       as if they are Latin-1 characters.  For example, "isSPACE_L1()" will return true when called with the code
       point 0xA0, which is the Latin-1 NO-BREAK SPACE.

       For EBCDIC platforms, the base function with no suffix and the one with the "_L1" suffix should be identical,
       since, as of this writing, the EBCDIC code pages that Perl knows about all are equivalent to Latin-1.  The
       function that ends in an "_A" suffix will not return true unless the specified character also has an ASCII
       equivalent.

       isALPHA Returns a boolean indicating whether the specified character is an alphabetic character in the
               platform's native character set.  See the top of this section for an explanation of variants
               "isALPHA_A" and "isALPHA_L1".

                       bool    isDIGIT(char ch)

       isLOWER Returns a boolean indicating whether the specified character is a lowercase character in the
               platform's native character set.  See the top of this section for an explanation of variants
               "isLOWER_A" and "isLOWER_L1".

                       bool    isLOWER(char ch)

       isOCTAL Returns a boolean indicating whether the specified character is an octal digit, [0-7] in the
               platform's native character set.  Variants "isOCTAL_A" and "isOCTAL_L1" are identical to "isOCTAL".

                       bool    isOCTAL(char ch)

       isSPACE Returns a boolean indicating whether the specified character is a whitespace character in the
               platform's native character set.  This is the same as what "\s" matches in a regular expression.  See
               the top of this section for an explanation of variants "isSPACE_A" and "isSPACE_L1".

                       bool    isSPACE(char ch)

       isUPPER Returns a boolean indicating whether the specified character is an uppercase character in the
               platform's native character set.  See the top of this section for an explanation of variants
               "isUPPER_A" and "isUPPER_L1".

                       bool    isUPPER(char ch)

       isWORDCHAR
               Returns a boolean indicating whether the specified character is a character that is any of:
               alphabetic, numeric, or an underscore.  This is the same as what "\w" matches in a regular expression.
               "isALNUM()" is a synonym provided for backward compatibility.  Note that it does not have the standard
               C language meaning of alphanumeric, since it matches an underscore and the standard meaning does not.
               See the top of this section for an explanation of variants "isWORDCHAR_A" and "isWORDCHAR_L1".

                       bool    isWORDCHAR(char ch)

       isXDIGIT
               Returns a boolean indicating whether the specified character is a hexadecimal digit, [0-9A-Fa-f].
               Variants "isXDIGIT_A()" and "isXDIGIT_L1()" are identical to "isXDIGIT()".

                       bool    isXDIGIT(char ch)

Cloning an interpreter
       perl_clone
               Create and return a new interpreter by cloning the current one.

               perl_clone takes these flags as parameters:

               CLONEf_COPY_STACKS - is used to, well, copy the stacks also, without it we only clone the data and
               zero the stacks, with it we copy the stacks and the new perl interpreter is ready to run at the exact
               same point as the previous one.  The pseudo-fork code uses COPY_STACKS while the threads->create
               doesn't.

               CLONEf_KEEP_PTR_TABLE - perl_clone keeps a ptr_table with the pointer of the old variable as a key and
               the new variable as a value, this allows it to check if something has been cloned and not clone it
               again but rather just use the value and increase the refcount.  If KEEP_PTR_TABLE is not set then

                                        )

Compile-time scope hooks
       BhkDISABLE
               Temporarily disable an entry in this BHK structure, by clearing the appropriate flag. which is a
               preprocessor token indicating which entry to disable.

               NOTE: this function is experimental and may change or be removed without notice.

                       void    BhkDISABLE(BHK *hk, which)

       BhkENABLE
               Re-enable an entry in this BHK structure, by setting the appropriate flag. which is a preprocessor
               token indicating which entry to enable.  This will assert (under -DDEBUGGING) if the entry doesn't
               contain a valid pointer.

               NOTE: this function is experimental and may change or be removed without notice.

                       void    BhkENABLE(BHK *hk, which)

       BhkENTRY_set
               Set an entry in the BHK structure, and set the flags to indicate it is valid. which is a preprocessing
               token indicating which entry to set.  The type of ptr depends on the entry.

               NOTE: this function is experimental and may change or be removed without notice.

                       void    BhkENTRY_set(BHK *hk, which, void *ptr)

       blockhook_register
               Register a set of hooks to be called when the Perl lexical scope changes at compile time. See
               "Compile-time scope hooks" in perlguts.

               NOTE: this function is experimental and may change or be removed without notice.

               NOTE: this function must be explicitly called as Perl_blockhook_register with an aTHX_ parameter.

                       void    Perl_blockhook_register(pTHX_ BHK *hk)

COP Hint Hashes
       cophh_2hv
               Generates and returns a standard Perl hash representing the full set of key/value pairs in the cop
               hints hash cophh.  flags is currently unused and must be zero.

               NOTE: this function is experimental and may change or be removed without notice.

                       HV *    cophh_2hv(const COPHH *cophh, U32 flags)

       cophh_copy
               Make and return a complete copy of the cop hints hash cophh.

               NOTE: this function is experimental and may change or be removed without notice.

                       COPHH * cophh_copy(COPHH *cophh)


               input hash is consumed by the function, and the pointer to it must not be subsequently used.  Use
               "cophh_copy" if you need both hashes.

               The key is specified by keypv and keylen.  If flags has the "COPHH_KEY_UTF8" bit set, the key octets
               are interpreted as UTF-8, otherwise they are interpreted as Latin-1.  hash is a precomputed hash of
               the key string, or zero if it has not been precomputed.

               NOTE: this function is experimental and may change or be removed without notice.

                       COPHH * cophh_delete_pvn(COPHH *cophh,
                                                const char *keypv,
                                                STRLEN keylen, U32 hash,
                                                U32 flags)

       cophh_delete_pvs
               Like "cophh_delete_pvn", but takes a literal string instead of a string/length pair, and no
               precomputed hash.

               NOTE: this function is experimental and may change or be removed without notice.

                       COPHH * cophh_delete_pvs(const COPHH *cophh,
                                                const char *key, U32 flags)

       cophh_delete_sv
               Like "cophh_delete_pvn", but takes a Perl scalar instead of a string/length pair.

               NOTE: this function is experimental and may change or be removed without notice.

                       COPHH * cophh_delete_sv(const COPHH *cophh, SV *key,
                                               U32 hash, U32 flags)

       cophh_fetch_pv
               Like "cophh_fetch_pvn", but takes a nul-terminated string instead of a string/length pair.

               NOTE: this function is experimental and may change or be removed without notice.

                       SV *    cophh_fetch_pv(const COPHH *cophh,
                                              const char *key, U32 hash,
                                              U32 flags)

       cophh_fetch_pvn
               Look up the entry in the cop hints hash cophh with the key specified by keypv and keylen.  If flags
               has the "COPHH_KEY_UTF8" bit set, the key octets are interpreted as UTF-8, otherwise they are
               interpreted as Latin-1.  hash is a precomputed hash of the key string, or zero if it has not been
               precomputed.  Returns a mortal scalar copy of the value associated with the key, or &PL_sv_placeholder
               if there is no value associated with the key.

               NOTE: this function is experimental and may change or be removed without notice.

                       SV *    cophh_fetch_pvn(const COPHH *cophh,
                                               const char *keypv,
                                               STRLEN keylen, U32 hash,
                                               U32 flags)


               NOTE: this function is experimental and may change or be removed without notice.

                       SV *    cophh_fetch_sv(const COPHH *cophh, SV *key,
                                              U32 hash, U32 flags)

       cophh_free
               Discard the cop hints hash cophh, freeing all resources associated with it.

               NOTE: this function is experimental and may change or be removed without notice.

                       void    cophh_free(COPHH *cophh)

       cophh_new_empty
               Generate and return a fresh cop hints hash containing no entries.

               NOTE: this function is experimental and may change or be removed without notice.

                       COPHH * cophh_new_empty()

       cophh_store_pv
               Like "cophh_store_pvn", but takes a nul-terminated string instead of a string/length pair.

               NOTE: this function is experimental and may change or be removed without notice.

                       COPHH * cophh_store_pv(const COPHH *cophh,
                                              const char *key, U32 hash,
                                              SV *value, U32 flags)

       cophh_store_pvn
               Stores a value, associated with a key, in the cop hints hash cophh, and returns the modified hash.
               The returned hash pointer is in general not the same as the hash pointer that was passed in.  The
               input hash is consumed by the function, and the pointer to it must not be subsequently used.  Use
               "cophh_copy" if you need both hashes.

               The key is specified by keypv and keylen.  If flags has the "COPHH_KEY_UTF8" bit set, the key octets
               are interpreted as UTF-8, otherwise they are interpreted as Latin-1.  hash is a precomputed hash of
               the key string, or zero if it has not been precomputed.

               value is the scalar value to store for this key.  value is copied by this function, which thus does
               not take ownership of any reference to it, and later changes to the scalar will not be reflected in
               the value visible in the cop hints hash.  Complex types of scalar will not be stored with referential
               integrity, but will be coerced to strings.

               NOTE: this function is experimental and may change or be removed without notice.

                       COPHH * cophh_store_pvn(COPHH *cophh, const char *keypv,
                                               STRLEN keylen, U32 hash,
                                               SV *value, U32 flags)

       cophh_store_pvs
               Like "cophh_store_pvn", but takes a literal string instead of a string/length pair, and no precomputed
               hash.

               NOTE: this function is experimental and may change or be removed without notice.

COP Hint Reading
       cop_hints_2hv
               Generates and returns a standard Perl hash representing the full set of hint entries in the cop cop.
               flags is currently unused and must be zero.

                       HV *    cop_hints_2hv(const COP *cop, U32 flags)

       cop_hints_fetch_pv
               Like "cop_hints_fetch_pvn", but takes a nul-terminated string instead of a string/length pair.

                       SV *    cop_hints_fetch_pv(const COP *cop,
                                                  const char *key, U32 hash,
                                                  U32 flags)

       cop_hints_fetch_pvn
               Look up the hint entry in the cop cop with the key specified by keypv and keylen.  If flags has the
               "COPHH_KEY_UTF8" bit set, the key octets are interpreted as UTF-8, otherwise they are interpreted as
               Latin-1.  hash is a precomputed hash of the key string, or zero if it has not been precomputed.
               Returns a mortal scalar copy of the value associated with the key, or &PL_sv_placeholder if there is
               no value associated with the key.

                       SV *    cop_hints_fetch_pvn(const COP *cop,
                                                   const char *keypv,
                                                   STRLEN keylen, U32 hash,
                                                   U32 flags)

       cop_hints_fetch_pvs
               Like "cop_hints_fetch_pvn", but takes a literal string instead of a string/length pair, and no
               precomputed hash.

                       SV *    cop_hints_fetch_pvs(const COP *cop,
                                                   const char *key, U32 flags)

       cop_hints_fetch_sv
               Like "cop_hints_fetch_pvn", but takes a Perl scalar instead of a string/length pair.

                       SV *    cop_hints_fetch_sv(const COP *cop, SV *key,
                                                  U32 hash, U32 flags)

Custom Operators
       custom_op_register
               Register a custom op. See "Custom Operators" in perlguts.

               NOTE: this function must be explicitly called as Perl_custom_op_register with an aTHX_ parameter.

                       void    Perl_custom_op_register(pTHX_
                                                       Perl_ppaddr_t ppaddr,
                                                       const XOP *xop)

       custom_op_xop
               Return the XOP structure for a given custom op. This function should be considered internal to OP_NAME
               and the other access macros: use them instead.


                       void    XopENABLE(XOP *xop, which)

       XopENTRY
               Return a member of the XOP structure. which is a cpp token indicating which entry to return. If the
               member is not set this will return a default value. The return type depends on which.

                               XopENTRY(XOP *xop, which)

       XopENTRY_set
               Set a member of the XOP structure. which is a cpp token indicating which entry to set. See "Custom
               Operators" in perlguts for details about the available members and how they are used.

                       void    XopENTRY_set(XOP *xop, which, value)

       XopFLAGS
               Return the XOP's flags.

                       U32     XopFLAGS(XOP *xop)

CV Manipulation Functions
       CvSTASH Returns the stash of the CV. A stash is the symbol table hash, containing the package-scoped variables
               in the package where the subroutine was defined.  For more information, see perlguts.

               This also has a special use with XS AUTOLOAD subs.  See "Autoloading with XSUBs" in perlguts.

                       HV*     CvSTASH(CV* cv)

       get_cv  Uses "strlen" to get the length of "name", then calls "get_cvn_flags".

               NOTE: the perl_ form of this function is deprecated.

                       CV*     get_cv(const char* name, I32 flags)

       get_cvn_flags
               Returns the CV of the specified Perl subroutine.  "flags" are passed to "gv_fetchpvn_flags". If
               "GV_ADD" is set and the Perl subroutine does not exist then it will be declared (which has the same
               effect as saying "sub name;").  If "GV_ADD" is not set and the subroutine does not exist then NULL is
               returned.

               NOTE: the perl_ form of this function is deprecated.

                       CV*     get_cvn_flags(const char* name, STRLEN len,
                                             I32 flags)

Embedding Functions
       cv_clone
               Clone a CV, making a lexical closure.  proto supplies the prototype of the function: its code, pad
               structure, and other attributes.  The prototype is combined with a capture of outer lexicals to which
               the code refers, which are taken from the currently-executing instance of the immediately surrounding
               code.

                       CV *    cv_clone(CV *proto)

       cv_undef
       find_rundefsvoffset
               Find the position of the lexical $_ in the pad of the currently-executing function.  Returns the
               offset in the current pad, or "NOT_IN_PAD" if there is no lexical $_ in scope (in which case the
               global one should be used instead).  "find_rundefsv" is likely to be more convenient.

               NOTE: the perl_ form of this function is deprecated.

                       PADOFFSET find_rundefsvoffset()

       load_module
               Loads the module whose name is pointed to by the string part of name.  Note that the actual module
               name, not its filename, should be given.  Eg, "Foo::Bar" instead of "Foo/Bar.pm".  flags can be any of
               PERL_LOADMOD_DENY, PERL_LOADMOD_NOIMPORT, or PERL_LOADMOD_IMPORT_OPS (or 0 for no flags). ver, if
               specified and not NULL, provides version semantics similar to "use Foo::Bar VERSION".  The optional
               trailing SV* arguments can be used to specify arguments to the module's import() method, similar to
               "use Foo::Bar VERSION LIST".  They must be terminated with a final NULL pointer.  Note that this list
               can only be omitted when the PERL_LOADMOD_NOIMPORT flag has been used.  Otherwise at least a single
               NULL pointer to designate the default import list is required.

               The reference count for each specified "SV*" parameter is decremented.

                       void    load_module(U32 flags, SV* name, SV* ver, ...)

       nothreadhook
               Stub that provides thread hook for perl_destruct when there are no threads.

                       int     nothreadhook()

       pad_add_anon
               Allocates a place in the currently-compiling pad (via "pad_alloc") for an anonymous function that is
               lexically scoped inside the currently-compiling function.  The function func is linked into the pad,
               and its "CvOUTSIDE" link to the outer scope is weakened to avoid a reference loop.

               optype should be an opcode indicating the type of operation that the pad entry is to support.  This
               doesn't affect operational semantics, but is used for debugging.

                       PADOFFSET pad_add_anon(CV *func, I32 optype)

       pad_add_name_pv
               Exactly like "pad_add_name_pvn", but takes a nul-terminated string instead of a string/length pair.

                       PADOFFSET pad_add_name_pv(const char *name, U32 flags,
                                                 HV *typestash, HV *ourstash)

       pad_add_name_pvn
               Allocates a place in the currently-compiling pad for a named lexical variable.  Stores the name and
               other metadata in the name part of the pad, and makes preparations to manage the variable's lexical
               scoping.  Returns the offset of the allocated pad slot.

               namepv/namelen specify the variable's name, including leading sigil.  If typestash is non-null, the
               name is for a typed lexical, and this identifies the type.  If ourstash is non-null, it's a lexical
               reference to a package variable, and this identifies the package.  The following flags can be OR'ed
               together:


                       PADOFFSET pad_add_name_sv(SV *name, U32 flags,
                                                 HV *typestash, HV *ourstash)

       pad_alloc
               Allocates a place in the currently-compiling pad, returning the offset of the allocated pad slot.  No
               name is initially attached to the pad slot.  tmptype is a set of flags indicating the kind of pad
               entry required, which will be set in the value SV for the allocated pad entry:

                   SVs_PADMY    named lexical variable ("my", "our", "state")
                   SVs_PADTMP   unnamed temporary store

               optype should be an opcode indicating the type of operation that the pad entry is to support.  This
               doesn't affect operational semantics, but is used for debugging.

               NOTE: this function is experimental and may change or be removed without notice.

                       PADOFFSET pad_alloc(I32 optype, U32 tmptype)

       pad_compname_type
               Looks up the type of the lexical variable at position po in the currently-compiling pad.  If the
               variable is typed, the stash of the class to which it is typed is returned.  If not, "NULL" is
               returned.

                       HV *    pad_compname_type(PADOFFSET po)

       pad_findmy_pv
               Exactly like "pad_findmy_pvn", but takes a nul-terminated string instead of a string/length pair.

                       PADOFFSET pad_findmy_pv(const char *name, U32 flags)

       pad_findmy_pvn
               Given the name of a lexical variable, find its position in the currently-compiling pad.
               namepv/namelen specify the variable's name, including leading sigil.  flags is reserved and must be
               zero.  If it is not in the current pad but appears in the pad of any lexically enclosing scope, then a
               pseudo-entry for it is added in the current pad.  Returns the offset in the current pad, or
               "NOT_IN_PAD" if no such lexical is in scope.

                       PADOFFSET pad_findmy_pvn(const char *namepv,
                                                STRLEN namelen, U32 flags)

       pad_findmy_sv
               Exactly like "pad_findmy_pvn", but takes the name string in the form of an SV instead of a
               string/length pair.

                       PADOFFSET pad_findmy_sv(SV *name, U32 flags)

       pad_setsv
               Set the value at offset po in the current (compiling or executing) pad.  Use the macro PAD_SETSV()
               rather than calling this function directly.

                       void    pad_setsv(PADOFFSET po, SV *sv)

       pad_sv  Get the value at offset po in the current (compiling or executing) pad.  Use macro PAD_SV instead of
               calling this function directly.
               NOTE: this function is experimental and may change or be removed without notice.

                       void    pad_tidy(padtidy_type type)

       perl_alloc
               Allocates a new Perl interpreter.  See perlembed.

                       PerlInterpreter* perl_alloc()

       perl_construct
               Initializes a new Perl interpreter.  See perlembed.

                       void    perl_construct(PerlInterpreter *my_perl)

       perl_destruct
               Shuts down a Perl interpreter.  See perlembed.

                       int     perl_destruct(PerlInterpreter *my_perl)

       perl_free
               Releases a Perl interpreter.  See perlembed.

                       void    perl_free(PerlInterpreter *my_perl)

       perl_parse
               Tells a Perl interpreter to parse a Perl script.  See perlembed.

                       int     perl_parse(PerlInterpreter *my_perl,
                                          XSINIT_t xsinit, int argc,
                                          char** argv, char** env)

       perl_run
               Tells a Perl interpreter to run.  See perlembed.

                       int     perl_run(PerlInterpreter *my_perl)

       require_pv
               Tells Perl to "require" the file named by the string argument.  It is analogous to the Perl code "eval
               "require '$file'"".  It's even implemented that way; consider using load_module instead.

               NOTE: the perl_ form of this function is deprecated.

                       void    require_pv(const char* pv)

Functions in file dump.c
       pv_display
               Similar to

                 pv_escape(dsv,pv,cur,pvlim,PERL_PV_ESCAPE_QUOTE);

               except that an additional "\0" will be appended to the string when len > cur and pv[cur] is "\0".

               Note that the final string may be up to 7 chars longer than pvlim.

               If PERL_PV_ESCAPE_UNI is set then the input string is treated as Unicode, if PERL_PV_ESCAPE_UNI_DETECT
               is set then the input string is scanned using "is_utf8_string()" to determine if it is Unicode.

               If PERL_PV_ESCAPE_ALL is set then all input chars will be output using "\x01F1" style escapes,
               otherwise if PERL_PV_ESCAPE_NONASCII is set, only chars above 127 will be escaped using this style;
               otherwise, only chars above 255 will be so escaped; other non printable chars will use octal or common
               escaped patterns like "\n". Otherwise, if PERL_PV_ESCAPE_NOBACKSLASH then all chars below 255 will be
               treated as printable and will be output as literals.

               If PERL_PV_ESCAPE_FIRSTCHAR is set then only the first char of the string will be escaped, regardless
               of max. If the output is to be in hex, then it will be returned as a plain hex sequence. Thus the
               output will either be a single char, an octal escape sequence, a special escape like "\n" or a hex
               value.

               If PERL_PV_ESCAPE_RE is set then the escape char used will be a '%' and not a '\\'. This is because
               regexes very often contain backslashed sequences, whereas '%' is not a particularly common character
               in patterns.

               Returns a pointer to the escaped text as held by dsv.

                       char*   pv_escape(SV *dsv, char const * const str,
                                         const STRLEN count, const STRLEN max,
                                         STRLEN * const escaped,
                                         const U32 flags)

       pv_pretty
               Converts a string into something presentable, handling escaping via pv_escape() and supporting quoting
               and ellipses.

               If the PERL_PV_PRETTY_QUOTE flag is set then the result will be double quoted with any double quotes
               in the string escaped. Otherwise if the PERL_PV_PRETTY_LTGT flag is set then the result be wrapped in
               angle brackets.

               If the PERL_PV_PRETTY_ELLIPSES flag is set and not all characters in string were output then an
               ellipsis "..." will be appended to the string. Note that this happens AFTER it has been quoted.

               If start_color is non-null then it will be inserted after the opening quote (if there is one) but
               before the escaped text. If end_color is non-null then it will be inserted after the escaped text but
               before any quotes or ellipses.

               Returns a pointer to the prettified text as held by dsv.

                       char*   pv_pretty(SV *dsv, char const * const str,
                                         const STRLEN count, const STRLEN max,
                                         char const * const start_color,
                                         char const * const end_color,
                                         const U32 flags)

Functions in file mathoms.c
       custom_op_desc
               Return the description of a given custom op. This was once used by the OP_DESC macro, but is no
               longer: it has only been kept for compatibility, and should not be used.

                       const char * custom_op_desc(const OP *o)

       pack_cat
               The engine implementing pack() Perl function. Note: parameters next_in_list and flags are not used.
               This call should not be used; use packlist instead.

                       void    pack_cat(SV *cat, const char *pat,
                                        const char *patend, SV **beglist,
                                        SV **endlist, SV ***next_in_list,
                                        U32 flags)

       sv_2pvbyte_nolen
               Return a pointer to the byte-encoded representation of the SV.  May cause the SV to be downgraded from
               UTF-8 as a side-effect.

               Usually accessed via the "SvPVbyte_nolen" macro.

                       char*   sv_2pvbyte_nolen(SV* sv)

       sv_2pvutf8_nolen
               Return a pointer to the UTF-8-encoded representation of the SV.  May cause the SV to be upgraded to
               UTF-8 as a side-effect.

               Usually accessed via the "SvPVutf8_nolen" macro.

                       char*   sv_2pvutf8_nolen(SV* sv)

       sv_2pv_nolen
               Like "sv_2pv()", but doesn't return the length too. You should usually use the macro wrapper
               "SvPV_nolen(sv)" instead.

                       char*   sv_2pv_nolen(SV* sv)

       sv_catpvn_mg
               Like "sv_catpvn", but also handles 'set' magic.

                       void    sv_catpvn_mg(SV *sv, const char *ptr,
                                            STRLEN len)

       sv_catsv_mg
               Like "sv_catsv", but also handles 'set' magic.

                       void    sv_catsv_mg(SV *dsv, SV *ssv)

       sv_force_normal
               Undo various types of fakery on an SV: if the PV is a shared string, make a private copy; if we're a
               ref, stop refing; if we're a glob, downgrade to an xpvmg. See also "sv_force_normal_flags".

                       void    sv_force_normal(SV *sv)

       sv_iv   A private implementation of the "SvIVx" macro for compilers which can't cope with complex macro
               expressions. Always use the macro instead.

                       IV      sv_iv(SV* sv)

       sv_nolocking

                       void    sv_nounlocking(SV *sv)

       sv_nv   A private implementation of the "SvNVx" macro for compilers which can't cope with complex macro
               expressions. Always use the macro instead.

                       NV      sv_nv(SV* sv)

       sv_pv   Use the "SvPV_nolen" macro instead

                       char*   sv_pv(SV *sv)

       sv_pvbyte
               Use "SvPVbyte_nolen" instead.

                       char*   sv_pvbyte(SV *sv)

       sv_pvbyten
               A private implementation of the "SvPVbyte" macro for compilers which can't cope with complex macro
               expressions. Always use the macro instead.

                       char*   sv_pvbyten(SV *sv, STRLEN *lp)

       sv_pvn  A private implementation of the "SvPV" macro for compilers which can't cope with complex macro
               expressions. Always use the macro instead.

                       char*   sv_pvn(SV *sv, STRLEN *lp)

       sv_pvutf8
               Use the "SvPVutf8_nolen" macro instead

                       char*   sv_pvutf8(SV *sv)

       sv_pvutf8n
               A private implementation of the "SvPVutf8" macro for compilers which can't cope with complex macro
               expressions. Always use the macro instead.

                       char*   sv_pvutf8n(SV *sv, STRLEN *lp)

       sv_taint
               Taint an SV. Use "SvTAINTED_on" instead.

                       void    sv_taint(SV* sv)

       sv_unref
               Unsets the RV status of the SV, and decrements the reference count of whatever was being referenced by
               the RV.  This can almost be thought of as a reversal of "newSVrv".  This is "sv_unref_flags" with the
               "flag" being zero.  See "SvROK_off".

                       void    sv_unref(SV* sv)

       sv_usepvn
               Tells an SV to use "ptr" to find its string value. Implemented by calling "sv_usepvn_flags" with
               "flags" of 0, hence does not handle 'set' magic. See "sv_usepvn_flags".

       unpack_str
               The engine implementing unpack() Perl function. Note: parameters strbeg, new_s and ocnt are not used.
               This call should not be used, use unpackstring instead.

                       I32     unpack_str(const char *pat, const char *patend,
                                          const char *s, const char *strbeg,
                                          const char *strend, char **new_s,
                                          I32 ocnt, U32 flags)

Functions in file op.c
       op_contextualize
               Applies a syntactic context to an op tree representing an expression.  o is the op tree, and context
               must be "G_SCALAR", "G_ARRAY", or "G_VOID" to specify the context to apply.  The modified op tree is
               returned.

                       OP *    op_contextualize(OP *o, I32 context)

Functions in file perl.h
       PERL_SYS_INIT
               Provides system-specific tune up of the C runtime environment necessary to run Perl interpreters. This
               should be called only once, before creating any Perl interpreters.

                       void    PERL_SYS_INIT(int argc, char** argv)

       PERL_SYS_INIT3
               Provides system-specific tune up of the C runtime environment necessary to run Perl interpreters. This
               should be called only once, before creating any Perl interpreters.

                       void    PERL_SYS_INIT3(int argc, char** argv,
                                              char** env)

       PERL_SYS_TERM
               Provides system-specific clean up of the C runtime environment after running Perl interpreters. This
               should be called only once, after freeing any remaining Perl interpreters.

                       void    PERL_SYS_TERM()

Functions in file pp_ctl.c
       caller_cx
               The XSUB-writer's equivalent of caller(). The returned "PERL_CONTEXT" structure can be interrogated to
               find all the information returned to Perl by "caller". Note that XSUBs don't get a stack frame, so
               "caller_cx(0, NULL)" will return information for the immediately-surrounding Perl code.

               This function skips over the automatic calls to &DB::sub made on the behalf of the debugger. If the
               stack frame requested was a sub called by "DB::sub", the return value will be the frame for the call
               to "DB::sub", since that has the correct line number/etc. for the call site. If dbcxp is non-"NULL",
               it will be set to a pointer to the frame for the sub call itself.

                       const PERL_CONTEXT * caller_cx(
                                                I32 level,
                                                const PERL_CONTEXT **dbcxp
                                            )


                       void    packlist(SV *cat, const char *pat,
                                        const char *patend, SV **beglist,
                                        SV **endlist)

       unpackstring
               The engine implementing unpack() Perl function. "unpackstring" puts the extracted list items on the
               stack and returns the number of elements.  Issue "PUTBACK" before and "SPAGAIN" after the call to this
               function.

                       I32     unpackstring(const char *pat,
                                            const char *patend, const char *s,
                                            const char *strend, U32 flags)

Functions in file pp_sys.c
       setdefout
               Sets PL_defoutgv, the default file handle for output, to the passed in typeglob. As PL_defoutgv "owns"
               a reference on its typeglob, the reference count of the passed in typeglob is increased by one, and
               the reference count of the typeglob that PL_defoutgv points to is decreased by one.

                       void    setdefout(GV* gv)

Functions in file utf8.h
       ibcmp_utf8
               This is a synonym for (! foldEQ_utf8())

                       I32     ibcmp_utf8(const char *s1, char **pe1, UV l1,
                                          bool u1, const char *s2, char **pe2,
                                          UV l2, bool u2)

Functions in file util.h
       ibcmp   This is a synonym for (! foldEQ())

                       I32     ibcmp(const char* a, const char* b, I32 len)

       ibcmp_locale
               This is a synonym for (! foldEQ_locale())

                       I32     ibcmp_locale(const char* a, const char* b,
                                            I32 len)

Global Variables
       PL_check
               Array, indexed by opcode, of functions that will be called for the "check" phase of optree building
               during compilation of Perl code.  For most (but not all) types of op, once the op has been initially
               built and populated with child ops it will be filtered through the check function referenced by the
               appropriate element of this array.  The new op is passed in as the sole argument to the check
               function, and the check function returns the completed op.  The check function may (as the name
               suggests) check the op for validity and signal errors.  It may also initialise or modify parts of the
               ops, or perform more radical surgery such as adding or removing child ops, or even throw the op away
               and return a different op in its place.

               This array of function pointers is a convenient place to hook into the compilation process.  An XS
               module can put its own custom check function in place of any of the standard ones, to influence the
               compilation of a particular type of op.  However, a custom check function must never fully replace a

                       int keyword_plugin_function(pTHX_
                               char *keyword_ptr, STRLEN keyword_len,
                               OP **op_ptr)

               The function is called from the tokeniser, whenever a possible keyword is seen.  "keyword_ptr" points
               at the word in the parser's input buffer, and "keyword_len" gives its length; it is not null-
               terminated.  The function is expected to examine the word, and possibly other state such as %^H, to
               decide whether it wants to handle it as an extended keyword.  If it does not, the function should
               return "KEYWORD_PLUGIN_DECLINE", and the normal parser process will continue.

               If the function wants to handle the keyword, it first must parse anything following the keyword that
               is part of the syntax introduced by the keyword.  See "Lexer interface" for details.

               When a keyword is being handled, the plugin function must build a tree of "OP" structures,
               representing the code that was parsed.  The root of the tree must be stored in *op_ptr.  The function
               then returns a constant indicating the syntactic role of the construct that it has parsed:
               "KEYWORD_PLUGIN_STMT" if it is a complete statement, or "KEYWORD_PLUGIN_EXPR" if it is an expression.
               Note that a statement construct cannot be used inside an expression (except via "do BLOCK" and
               similar), and an expression is not a complete statement (it requires at least a terminating
               semicolon).

               When a keyword is handled, the plugin function may also have (compile-time) side effects.  It may
               modify "%^H", define functions, and so on.  Typically, if side effects are the main purpose of a
               handler, it does not wish to generate any ops to be included in the normal compilation.  In this case
               it is still required to supply an op tree, but it suffices to generate a single null op.

               That's how the *PL_keyword_plugin function needs to behave overall.  Conventionally, however, one does
               not completely replace the existing handler function.  Instead, take a copy of "PL_keyword_plugin"
               before assigning your own function pointer to it.  Your handler function should look for keywords that
               it is interested in and handle those.  Where it is not interested, it should call the saved plugin
               function, passing on the arguments it received.  Thus "PL_keyword_plugin" actually points at a chain
               of handler functions, all of which have an opportunity to handle keywords, and only the last function
               in the chain (built into the Perl core) will normally return "KEYWORD_PLUGIN_DECLINE".

               NOTE: this function is experimental and may change or be removed without notice.

GV Functions
       GvSV    Return the SV from the GV.

                       SV*     GvSV(GV* gv)

       gv_const_sv
               If "gv" is a typeglob whose subroutine entry is a constant sub eligible for inlining, or "gv" is a
               placeholder reference that would be promoted to such a typeglob, then returns the value returned by
               the sub.  Otherwise, returns NULL.

                       SV*     gv_const_sv(GV* gv)

       gv_fetchmeth
               Like "gv_fetchmeth_pvn", but lacks a flags parameter.

                       GV*     gv_fetchmeth(HV* stash, const char* name,
                                            STRLEN len, I32 level)

               returned glob for a long time, you need to check for it being "AUTOLOAD", since at the later time the
               call may load a different subroutine due to $AUTOLOAD changing its value. Use the glob created via a
               side effect to do this.

               These functions have the same side-effects and as "gv_fetchmeth" with "level==0".  "name" should be
               writable if contains ':' or ' ''. The warning against passing the GV returned by "gv_fetchmeth" to
               "call_sv" apply equally to these functions.

                       GV*     gv_fetchmethod_autoload(HV* stash,
                                                       const char* name,
                                                       I32 autoload)

       gv_fetchmeth_autoload
               This is the old form of "gv_fetchmeth_pvn_autoload", which has no flags parameter.

                       GV*     gv_fetchmeth_autoload(HV* stash,
                                                     const char* name,
                                                     STRLEN len, I32 level)

       gv_fetchmeth_pv
               Exactly like "gv_fetchmeth_pvn", but takes a nul-terminated string instead of a string/length pair.

                       GV*     gv_fetchmeth_pv(HV* stash, const char* name,
                                               I32 level, U32 flags)

       gv_fetchmeth_pvn
               Returns the glob with the given "name" and a defined subroutine or "NULL".  The glob lives in the
               given "stash", or in the stashes accessible via @ISA and UNIVERSAL::.

               The argument "level" should be either 0 or -1.  If "level==0", as a side-effect creates a glob with
               the given "name" in the given "stash" which in the case of success contains an alias for the
               subroutine, and sets up caching info for this glob.

               Currently, the only significant value for "flags" is SVf_UTF8.

               This function grants "SUPER" token as a postfix of the stash name. The GV returned from "gv_fetchmeth"
               may be a method cache entry, which is not visible to Perl code.  So when calling "call_sv", you should
               not use the GV directly; instead, you should use the method's CV, which can be obtained from the GV
               with the "GvCV" macro.

                       GV*     gv_fetchmeth_pvn(HV* stash, const char* name,
                                                STRLEN len, I32 level,
                                                U32 flags)

       gv_fetchmeth_pvn_autoload
               Same as gv_fetchmeth_pvn(), but looks for autoloaded subroutines too.  Returns a glob for the
               subroutine.

               For an autoloaded subroutine without a GV, will create a GV even if "level < 0".  For an autoloaded
               subroutine without a stub, GvCV() of the result may be zero.

               Currently, the only significant value for "flags" is SVf_UTF8.

                       GV*     gv_fetchmeth_pvn_autoload(HV* stash,

       gv_fetchmeth_sv
               Exactly like "gv_fetchmeth_pvn", but takes the name string in the form of an SV instead of a
               string/length pair.

                       GV*     gv_fetchmeth_sv(HV* stash, SV* namesv,
                                               I32 level, U32 flags)

       gv_fetchmeth_sv_autoload
               Exactly like "gv_fetchmeth_pvn_autoload", but takes the name string in the form of an SV instead of a
               string/length pair.

                       GV*     gv_fetchmeth_sv_autoload(HV* stash, SV* namesv,
                                                        I32 level, U32 flags)

       gv_init The old form of gv_init_pvn().  It does not work with UTF8 strings, as it has no flags parameter.  If
               the "multi" parameter is set, the GV_ADDMULTI flag will be passed to gv_init_pvn().

                       void    gv_init(GV* gv, HV* stash, const char* name,
                                       STRLEN len, int multi)

       gv_init_pv
               Same as gv_init_pvn(), but takes a nul-terminated string for the name instead of separate char * and
               length parameters.

                       void    gv_init_pv(GV* gv, HV* stash, const char* name,
                                          U32 flags)

       gv_init_pvn
               Converts a scalar into a typeglob.  This is an incoercible typeglob; assigning a reference to it will
               assign to one of its slots, instead of overwriting it as happens with typeglobs created by SvSetSV.
               Converting any scalar that is SvOK() may produce unpredictable results and is reserved for perl's
               internal use.

               "gv" is the scalar to be converted.

               "stash" is the parent stash/package, if any.

               "name" and "len" give the name.  The name must be unqualified; that is, it must not include the
               package name.  If "gv" is a stash element, it is the caller's responsibility to ensure that the name
               passed to this function matches the name of the element.  If it does not match, perl's internal
               bookkeeping will get out of sync.

               "flags" can be set to SVf_UTF8 if "name" is a UTF8 string, or the return value of SvUTF8(sv).  It can
               also take the GV_ADDMULTI flag, which means to pretend that the GV has been seen before (i.e.,
               suppress "Used once" warnings).

                       void    gv_init_pvn(GV* gv, HV* stash, const char* name,
                                           STRLEN len, U32 flags)

       gv_init_sv
               Same as gv_init_pvn(), but takes an SV * for the name instead of separate char * and length
               parameters.  "flags" is currently unused.

                       void    gv_init_sv(GV* gv, HV* stash, SV* namesv,

               (or any other setting that does not create packages) then NULL is returned.

                       HV*     gv_stashpvn(const char* name, U32 namelen,
                                           I32 flags)

       gv_stashpvs
               Like "gv_stashpvn", but takes a literal string instead of a string/length pair.

                       HV*     gv_stashpvs(const char* name, I32 create)

       gv_stashsv
               Returns a pointer to the stash for a specified package.  See "gv_stashpvn".

                       HV*     gv_stashsv(SV* sv, I32 flags)

Handy Values
       Nullav  Null AV pointer.

               (deprecated - use "(AV *)NULL" instead)

       Nullch  Null character pointer. (No longer available when "PERL_CORE" is defined.)

       Nullcv  Null CV pointer.

               (deprecated - use "(CV *)NULL" instead)

       Nullhv  Null HV pointer.

               (deprecated - use "(HV *)NULL" instead)

       Nullsv  Null SV pointer. (No longer available when "PERL_CORE" is defined.)

Hash Manipulation Functions
       cop_fetch_label
               Returns the label attached to a cop.  The flags pointer may be set to "SVf_UTF8" or 0.

               NOTE: this function is experimental and may change or be removed without notice.

                       const char * cop_fetch_label(COP *const cop,
                                                    STRLEN *len, U32 *flags)

       cop_store_label
               Save a label into a "cop_hints_hash". You need to set flags to "SVf_UTF8" for a utf-8 label.

               NOTE: this function is experimental and may change or be removed without notice.

                       void    cop_store_label(COP *const cop,
                                               const char *label, STRLEN len,
                                               U32 flags)

       get_hv  Returns the HV of the specified Perl hash.  "flags" are passed to "gv_fetchpv". If "GV_ADD" is set and
               the Perl variable does not exist then it will be created.  If "flags" is zero and the variable does
               not exist then NULL is returned.


       HeKEY   Returns the actual pointer stored in the key slot of the hash entry. The pointer may be either "char*"
               or "SV*", depending on the value of "HeKLEN()".  Can be assigned to.  The "HePV()" or "HeSVKEY()"
               macros are usually preferable for finding the value of a key.

                       void*   HeKEY(HE* he)

       HeKLEN  If this is negative, and amounts to "HEf_SVKEY", it indicates the entry holds an "SV*" key.
               Otherwise, holds the actual length of the key.  Can be assigned to. The "HePV()" macro is usually
               preferable for finding key lengths.

                       STRLEN  HeKLEN(HE* he)

       HePV    Returns the key slot of the hash entry as a "char*" value, doing any necessary dereferencing of
               possibly "SV*" keys.  The length of the string is placed in "len" (this is a macro, so do not use
               &len).  If you do not care about what the length of the key is, you may use the global variable
               "PL_na", though this is rather less efficient than using a local variable.  Remember though, that hash
               keys in perl are free to contain embedded nulls, so using "strlen()" or similar is not a good way to
               find the length of hash keys. This is very similar to the "SvPV()" macro described elsewhere in this
               document. See also "HeUTF8".

               If you are using "HePV" to get values to pass to "newSVpvn()" to create a new SV, you should consider
               using "newSVhek(HeKEY_hek(he))" as it is more efficient.

                       char*   HePV(HE* he, STRLEN len)

       HeSVKEY Returns the key as an "SV*", or "NULL" if the hash entry does not contain an "SV*" key.

                       SV*     HeSVKEY(HE* he)

       HeSVKEY_force
               Returns the key as an "SV*".  Will create and return a temporary mortal "SV*" if the hash entry
               contains only a "char*" key.

                       SV*     HeSVKEY_force(HE* he)

       HeSVKEY_set
               Sets the key to a given "SV*", taking care to set the appropriate flags to indicate the presence of an
               "SV*" key, and returns the same "SV*".

                       SV*     HeSVKEY_set(HE* he, SV* sv)

       HeUTF8  Returns whether the "char *" value returned by "HePV" is encoded in UTF-8, doing any necessary
               dereferencing of possibly "SV*" keys.  The value returned will be 0 or non-0, not necessarily 1 (or
               even a value with any low bits set), so do not blindly assign this to a "bool" variable, as "bool" may
               be a typedef for "char".

                       char*   HeUTF8(HE* he)

       HeVAL   Returns the value slot (type "SV*") stored in the hash entry.

                       SV*     HeVAL(HE* he)

       HvENAME Returns the effective name of a stash, or NULL if there is none. The effective name represents a

               Returns true if the effective name is in UTF8 encoding.

                       unsigned char HvENAMEUTF8(HV *stash)

       HvNAME  Returns the package name of a stash, or NULL if "stash" isn't a stash.  See "SvSTASH", "CvSTASH".

                       char*   HvNAME(HV* stash)

       HvNAMELEN
               Returns the length of the stash's name.

                       STRLEN  HvNAMELEN(HV *stash)

       HvNAMEUTF8
               Returns true if the name is in UTF8 encoding.

                       unsigned char HvNAMEUTF8(HV *stash)

       hv_assert
               Check that a hash is in an internally consistent state.

                       void    hv_assert(HV *hv)

       hv_clear
               Frees the all the elements of a hash, leaving it empty.  The XS equivalent of "%hash = ()".  See also
               "hv_undef".

               If any destructors are triggered as a result, the hv itself may be freed.

                       void    hv_clear(HV *hv)

       hv_clear_placeholders
               Clears any placeholders from a hash.  If a restricted hash has any of its keys marked as readonly and
               the key is subsequently deleted, the key is not actually deleted but is marked by assigning it a value
               of &PL_sv_placeholder.  This tags it so it will be ignored by future operations such as iterating over
               the hash, but will still allow the hash to have a value reassigned to the key at some future point.
               This function clears any such placeholder keys from the hash.  See Hash::Util::lock_keys() for an
               example of its use.

                       void    hv_clear_placeholders(HV *hv)

       hv_copy_hints_hv
               A specialised version of "newHVhv" for copying "%^H".  ohv must be a pointer to a hash (which may have
               "%^H" magic, but should be generally non-magical), or "NULL" (interpreted as an empty hash).  The
               content of ohv is copied to a new hash, which has the "%^H"-specific magic added to it.  A pointer to
               the new hash is returned.

                       HV *    hv_copy_hints_hv(HV *ohv)

       hv_delete
               Deletes a key/value pair in the hash.  The value's SV is removed from the hash, made mortal, and
               returned to the caller.  The absolute value of "klen" is the length of the key.  If "klen" is negative
               the key is assumed to be in UTF-8-encoded Unicode.  The "flags" value will normally be zero; if set to
               G_DISCARD then NULL will be returned.  NULL will also be returned if the key is not found.

       hv_exists
               Returns a boolean indicating whether the specified hash key exists.  The absolute value of "klen" is
               the length of the key.  If "klen" is negative the key is assumed to be in UTF-8-encoded Unicode.

                       bool    hv_exists(HV *hv, const char *key, I32 klen)

       hv_exists_ent
               Returns a boolean indicating whether the specified hash key exists.  "hash" can be a valid precomputed
               hash value, or 0 to ask for it to be computed.

                       bool    hv_exists_ent(HV *hv, SV *keysv, U32 hash)

       hv_fetch
               Returns the SV which corresponds to the specified key in the hash.  The absolute value of "klen" is
               the length of the key.  If "klen" is negative the key is assumed to be in UTF-8-encoded Unicode.  If
               "lval" is set then the fetch will be part of a store.  Check that the return value is non-null before
               dereferencing it to an "SV*".

               See "Understanding the Magic of Tied Hashes and Arrays" in perlguts for more information on how to use
               this function on tied hashes.

                       SV**    hv_fetch(HV *hv, const char *key, I32 klen,
                                        I32 lval)

       hv_fetchs
               Like "hv_fetch", but takes a literal string instead of a string/length pair.

                       SV**    hv_fetchs(HV* tb, const char* key, I32 lval)

       hv_fetch_ent
               Returns the hash entry which corresponds to the specified key in the hash.  "hash" must be a valid
               precomputed hash number for the given "key", or 0 if you want the function to compute it.  IF "lval"
               is set then the fetch will be part of a store.  Make sure the return value is non-null before
               accessing it.  The return value when "hv" is a tied hash is a pointer to a static location, so be sure
               to make a copy of the structure if you need to store it somewhere.

               See "Understanding the Magic of Tied Hashes and Arrays" in perlguts for more information on how to use
               this function on tied hashes.

                       HE*     hv_fetch_ent(HV *hv, SV *keysv, I32 lval,
                                            U32 hash)

       hv_fill Returns the number of hash buckets that happen to be in use. This function is wrapped by the macro
               "HvFILL".

               Previously this value was stored in the HV structure, rather than being calculated on demand.

                       STRLEN  hv_fill(HV const *const hv)

       hv_iterinit
               Prepares a starting point to traverse a hash table.  Returns the number of keys in the hash (i.e. the
               same as "HvUSEDKEYS(hv)").  The return value is currently only meaningful for hashes without tie
               magic.
               Returns the key as an "SV*" from the current position of the hash iterator.  The return value will
               always be a mortal copy of the key.  Also see "hv_iterinit".

                       SV*     hv_iterkeysv(HE* entry)

       hv_iternext
               Returns entries from a hash iterator.  See "hv_iterinit".

               You may call "hv_delete" or "hv_delete_ent" on the hash entry that the iterator currently points to,
               without losing your place or invalidating your iterator.  Note that in this case the current entry is
               deleted from the hash with your iterator holding the last reference to it.  Your iterator is flagged
               to free the entry on the next call to "hv_iternext", so you must not discard your iterator immediately
               else the entry will leak - call "hv_iternext" to trigger the resource deallocation.

                       HE*     hv_iternext(HV *hv)

       hv_iternextsv
               Performs an "hv_iternext", "hv_iterkey", and "hv_iterval" in one operation.

                       SV*     hv_iternextsv(HV *hv, char **key, I32 *retlen)

       hv_iternext_flags
               Returns entries from a hash iterator.  See "hv_iterinit" and "hv_iternext".  The "flags" value will
               normally be zero; if HV_ITERNEXT_WANTPLACEHOLDERS is set the placeholders keys (for restricted hashes)
               will be returned in addition to normal keys. By default placeholders are automatically skipped over.
               Currently a placeholder is implemented with a value that is &PL_sv_placeholder.  Note that the
               implementation of placeholders and restricted hashes may change, and the implementation currently is
               insufficiently abstracted for any change to be tidy.

               NOTE: this function is experimental and may change or be removed without notice.

                       HE*     hv_iternext_flags(HV *hv, I32 flags)

       hv_iterval
               Returns the value from the current position of the hash iterator.  See "hv_iterkey".

                       SV*     hv_iterval(HV *hv, HE *entry)

       hv_magic
               Adds magic to a hash.  See "sv_magic".

                       void    hv_magic(HV *hv, GV *gv, int how)

       hv_scalar
               Evaluates the hash in scalar context and returns the result. Handles magic when the hash is tied.

                       SV*     hv_scalar(HV *hv)

       hv_store
               Stores an SV in a hash.  The hash key is specified as "key" and the absolute value of "klen" is the
               length of the key.  If "klen" is negative the key is assumed to be in UTF-8-encoded Unicode.  The
               "hash" parameter is the precomputed hash value; if it is zero then Perl will compute it.

               The return value will be NULL if the operation failed or if the value did not need to be actually

                       SV**    hv_store(HV *hv, const char *key, I32 klen,
                                        SV *val, U32 hash)

       hv_stores
               Like "hv_store", but takes a literal string instead of a string/length pair and omits the hash
               parameter.

                       SV**    hv_stores(HV* tb, const char* key,
                                         NULLOK SV* val)

       hv_store_ent
               Stores "val" in a hash.  The hash key is specified as "key".  The "hash" parameter is the precomputed
               hash value; if it is zero then Perl will compute it.  The return value is the new hash entry so
               created.  It will be NULL if the operation failed or if the value did not need to be actually stored
               within the hash (as in the case of tied hashes).  Otherwise the contents of the return value can be
               accessed using the "He?" macros described here.  Note that the caller is responsible for suitably
               incrementing the reference count of "val" before the call, and decrementing it if the function
               returned NULL.  Effectively a successful hv_store_ent takes ownership of one reference to "val".  This
               is usually what you want; a newly created SV has a reference count of one, so if all your code does is
               create SVs then store them in a hash, hv_store will own the only reference to the new SV, and your
               code doesn't need to do anything further to tidy up.  Note that hv_store_ent only reads the "key";
               unlike "val" it does not take ownership of it, so maintaining the correct reference count on "key" is
               entirely the caller's responsibility.  hv_store is not implemented as a call to hv_store_ent, and does
               not create a temporary SV for the key, so if your key data is not already in SV form then use hv_store
               in preference to hv_store_ent.

               See "Understanding the Magic of Tied Hashes and Arrays" in perlguts for more information on how to use
               this function on tied hashes.

                       HE*     hv_store_ent(HV *hv, SV *key, SV *val, U32 hash)

       hv_undef
               Undefines the hash.  The XS equivalent of "undef(%hash)".

               As well as freeing all the elements of the hash (like hv_clear()), this also frees any auxiliary data
               and storage associated with the hash.

               If any destructors are triggered as a result, the hv itself may be freed.

               See also "hv_clear".

                       void    hv_undef(HV *hv)

       newHV   Creates a new HV.  The reference count is set to 1.

                       HV*     newHV()

Hook manipulation
       wrap_op_checker
               Puts a C function into the chain of check functions for a specified op type.  This is the preferred
               way to manipulate the "PL_check" array.  opcode specifies which type of op is to be affected.
               new_checker is a pointer to the C function that is to be added to that opcode's check chain, and
               old_checker_p points to the storage location where a pointer to the next function in the chain will be
               When this function is called, the function referenced by new_checker must be ready to be called,
               except for *old_checker_p being unfilled.  In a threading situation, new_checker may be called
               immediately, even before this function has returned.  *old_checker_p will always be appropriately set
               before new_checker is called.  If new_checker decides not to do anything special with an op that it is
               given (which is the usual case for most uses of op check hooking), it must chain the check function
               referenced by *old_checker_p.

               If you want to influence compilation of calls to a specific subroutine, then use "cv_set_call_checker"
               rather than hooking checking of all "entersub" ops.

                       void    wrap_op_checker(Optype opcode,
                                               Perl_check_t new_checker,
                                               Perl_check_t *old_checker_p)

Lexer interface
       lex_bufutf8
               Indicates whether the octets in the lexer buffer ("PL_parser->linestr") should be interpreted as the
               UTF-8 encoding of Unicode characters.  If not, they should be interpreted as Latin-1 characters.  This
               is analogous to the "SvUTF8" flag for scalars.

               In UTF-8 mode, it is not guaranteed that the lexer buffer actually contains valid UTF-8.  Lexing code
               must be robust in the face of invalid encoding.

               The actual "SvUTF8" flag of the "PL_parser->linestr" scalar is significant, but not the whole story
               regarding the input character encoding.  Normally, when a file is being read, the scalar contains
               octets and its "SvUTF8" flag is off, but the octets should be interpreted as UTF-8 if the "use utf8"
               pragma is in effect.  During a string eval, however, the scalar may have the "SvUTF8" flag on, and in
               this case its octets should be interpreted as UTF-8 unless the "use bytes" pragma is in effect.  This
               logic may change in the future; use this function instead of implementing the logic yourself.

               NOTE: this function is experimental and may change or be removed without notice.

                       bool    lex_bufutf8()

       lex_discard_to
               Discards the first part of the "PL_parser->linestr" buffer, up to ptr.  The remaining content of the
               buffer will be moved, and all pointers into the buffer updated appropriately.  ptr must not be later
               in the buffer than the position of "PL_parser->bufptr": it is not permitted to discard text that has
               yet to be lexed.

               Normally it is not necessarily to do this directly, because it suffices to use the implicit discarding
               behaviour of "lex_next_chunk" and things based on it.  However, if a token stretches across multiple
               lines, and the lexing code has kept multiple lines of text in the buffer for that purpose, then after
               completion of the token it would be wise to explicitly discard the now-unneeded earlier lines, to
               avoid future multi-line tokens growing the buffer without bound.

               NOTE: this function is experimental and may change or be removed without notice.

                       void    lex_discard_to(char *ptr)

       lex_grow_linestr
               Reallocates the lexer buffer ("PL_parser->linestr") to accommodate at least len octets (including
               terminating NUL).  Returns a pointer to the reallocated buffer.  This is necessary before making any
               direct modification of the buffer that would increase its length.  "lex_stuff_pvn" provides a more
               usual, but not necessary, for lexing to have consumed the entirety of the current chunk at this time.

               If "PL_parser->bufptr" is pointing to the very end of the current chunk (i.e., the current chunk has
               been entirely consumed), normally the current chunk will be discarded at the same time that the new
               chunk is read in.  If flags includes "LEX_KEEP_PREVIOUS", the current chunk will not be discarded.  If
               the current chunk has not been entirely consumed, then it will not be discarded regardless of the
               flag.

               Returns true if some new text was added to the buffer, or false if the buffer has reached the end of
               the input text.

               NOTE: this function is experimental and may change or be removed without notice.

                       bool    lex_next_chunk(U32 flags)

       lex_peek_unichar
               Looks ahead one (Unicode) character in the text currently being lexed.  Returns the codepoint
               (unsigned integer value) of the next character, or -1 if lexing has reached the end of the input text.
               To consume the peeked character, use "lex_read_unichar".

               If the next character is in (or extends into) the next chunk of input text, the next chunk will be
               read in.  Normally the current chunk will be discarded at the same time, but if flags includes
               "LEX_KEEP_PREVIOUS" then the current chunk will not be discarded.

               If the input is being interpreted as UTF-8 and a UTF-8 encoding error is encountered, an exception is
               generated.

               NOTE: this function is experimental and may change or be removed without notice.

                       I32     lex_peek_unichar(U32 flags)

       lex_read_space
               Reads optional spaces, in Perl style, in the text currently being lexed.  The spaces may include
               ordinary whitespace characters and Perl-style comments.  "#line" directives are processed if
               encountered.  "PL_parser->bufptr" is moved past the spaces, so that it points at a non-space character
               (or the end of the input text).

               If spaces extend into the next chunk of input text, the next chunk will be read in.  Normally the
               current chunk will be discarded at the same time, but if flags includes "LEX_KEEP_PREVIOUS" then the
               current chunk will not be discarded.

               NOTE: this function is experimental and may change or be removed without notice.

                       void    lex_read_space(U32 flags)

       lex_read_to
               Consume text in the lexer buffer, from "PL_parser->bufptr" up to ptr.  This advances
               "PL_parser->bufptr" to match ptr, performing the correct bookkeeping whenever a newline character is
               passed.  This is the normal way to consume lexed text.

               Interpretation of the buffer's octets can be abstracted out by using the slightly higher-level
               functions "lex_peek_unichar" and "lex_read_unichar".

               NOTE: this function is experimental and may change or be removed without notice.

               If the input is being interpreted as UTF-8 and a UTF-8 encoding error is encountered, an exception is
               generated.

               NOTE: this function is experimental and may change or be removed without notice.

                       I32     lex_read_unichar(U32 flags)

       lex_start
               Creates and initialises a new lexer/parser state object, supplying a context in which to lex and parse
               from a new source of Perl code.  A pointer to the new state object is placed in "PL_parser".  An entry
               is made on the save stack so that upon unwinding the new state object will be destroyed and the former
               value of "PL_parser" will be restored.  Nothing else need be done to clean up the parsing context.

               The code to be parsed comes from line and rsfp.  line, if non-null, provides a string (in SV form)
               containing code to be parsed.  A copy of the string is made, so subsequent modification of line does
               not affect parsing.  rsfp, if non-null, provides an input stream from which code will be read to be
               parsed.  If both are non-null, the code in line comes first and must consist of complete lines of
               input, and rsfp supplies the remainder of the source.

               The flags parameter is reserved for future use.  Currently it is only used by perl internally, so
               extensions should always pass zero.

               NOTE: this function is experimental and may change or be removed without notice.

                       void    lex_start(SV *line, PerlIO *rsfp, U32 flags)

       lex_stuff_pv
               Insert characters into the lexer buffer ("PL_parser->linestr"), immediately after the current lexing
               point ("PL_parser->bufptr"), reallocating the buffer if necessary.  This means that lexing code that
               runs later will see the characters as if they had appeared in the input.  It is not recommended to do
               this as part of normal parsing, and most uses of this facility run the risk of the inserted characters
               being interpreted in an unintended manner.

               The string to be inserted is represented by octets starting at pv and continuing to the first nul.
               These octets are interpreted as either UTF-8 or Latin-1, according to whether the "LEX_STUFF_UTF8"
               flag is set in flags.  The characters are recoded for the lexer buffer, according to how the buffer is
               currently being interpreted ("lex_bufutf8").  If it is not convenient to nul-terminate a string to be
               inserted, the "lex_stuff_pvn" function is more appropriate.

               NOTE: this function is experimental and may change or be removed without notice.

                       void    lex_stuff_pv(const char *pv, U32 flags)

       lex_stuff_pvn
               Insert characters into the lexer buffer ("PL_parser->linestr"), immediately after the current lexing
               point ("PL_parser->bufptr"), reallocating the buffer if necessary.  This means that lexing code that
               runs later will see the characters as if they had appeared in the input.  It is not recommended to do
               this as part of normal parsing, and most uses of this facility run the risk of the inserted characters
               being interpreted in an unintended manner.

               The string to be inserted is represented by len octets starting at pv.  These octets are interpreted
               as either UTF-8 or Latin-1, according to whether the "LEX_STUFF_UTF8" flag is set in flags.  The
               characters are recoded for the lexer buffer, according to how the buffer is currently being

                       void    lex_stuff_pvs(const char *pv, U32 flags)

       lex_stuff_sv
               Insert characters into the lexer buffer ("PL_parser->linestr"), immediately after the current lexing
               point ("PL_parser->bufptr"), reallocating the buffer if necessary.  This means that lexing code that
               runs later will see the characters as if they had appeared in the input.  It is not recommended to do
               this as part of normal parsing, and most uses of this facility run the risk of the inserted characters
               being interpreted in an unintended manner.

               The string to be inserted is the string value of sv.  The characters are recoded for the lexer buffer,
               according to how the buffer is currently being interpreted ("lex_bufutf8").  If a string to be
               inserted is not already a Perl scalar, the "lex_stuff_pvn" function avoids the need to construct a
               scalar.

               NOTE: this function is experimental and may change or be removed without notice.

                       void    lex_stuff_sv(SV *sv, U32 flags)

       lex_unstuff
               Discards text about to be lexed, from "PL_parser->bufptr" up to ptr.  Text following ptr will be
               moved, and the buffer shortened.  This hides the discarded text from any lexing code that runs later,
               as if the text had never appeared.

               This is not the normal way to consume lexed text.  For that, use "lex_read_to".

               NOTE: this function is experimental and may change or be removed without notice.

                       void    lex_unstuff(char *ptr)

       parse_arithexpr
               Parse a Perl arithmetic expression.  This may contain operators of precedence down to the bit shift
               operators.  The expression must be followed (and thus terminated) either by a comparison or lower-
               precedence operator or by something that would normally terminate an expression such as semicolon.  If
               flags includes "PARSE_OPTIONAL" then the expression is optional, otherwise it is mandatory.  It is up
               to the caller to ensure that the dynamic parser state ("PL_parser" et al) is correctly set to reflect
               the source of the code to be parsed and the lexical context for the expression.

               The op tree representing the expression is returned.  If an optional expression is absent, a null
               pointer is returned, otherwise the pointer will be non-null.

               If an error occurs in parsing or compilation, in most cases a valid op tree is returned anyway.  The
               error is reflected in the parser state, normally resulting in a single exception at the top level of
               parsing which covers all the compilation errors that occurred.  Some compilation errors, however, will
               throw an exception immediately.

               NOTE: this function is experimental and may change or be removed without notice.

                       OP *    parse_arithexpr(U32 flags)

       parse_barestmt
               Parse a single unadorned Perl statement.  This may be a normal imperative statement or a declaration
               that has compile-time effect.  It does not include any label or other affixture.  It is up to the
               caller to ensure that the dynamic parser state ("PL_parser" et al) is correctly set to reflect the

               The flags parameter is reserved for future use, and must always be zero.

               NOTE: this function is experimental and may change or be removed without notice.

                       OP *    parse_barestmt(U32 flags)

       parse_block
               Parse a single complete Perl code block.  This consists of an opening brace, a sequence of statements,
               and a closing brace.  The block constitutes a lexical scope, so "my" variables and various compile-
               time effects can be contained within it.  It is up to the caller to ensure that the dynamic parser
               state ("PL_parser" et al) is correctly set to reflect the source of the code to be parsed and the
               lexical context for the statement.

               The op tree representing the code block is returned.  This is always a real op, never a null pointer.
               It will normally be a "lineseq" list, including "nextstate" or equivalent ops.  No ops to construct
               any kind of runtime scope are included by virtue of it being a block.

               If an error occurs in parsing or compilation, in most cases a valid op tree (most likely null) is
               returned anyway.  The error is reflected in the parser state, normally resulting in a single exception
               at the top level of parsing which covers all the compilation errors that occurred.  Some compilation
               errors, however, will throw an exception immediately.

               The flags parameter is reserved for future use, and must always be zero.

               NOTE: this function is experimental and may change or be removed without notice.

                       OP *    parse_block(U32 flags)

       parse_fullexpr
               Parse a single complete Perl expression.  This allows the full expression grammar, including the
               lowest-precedence operators such as "or".  The expression must be followed (and thus terminated) by a
               token that an expression would normally be terminated by: end-of-file, closing bracketing punctuation,
               semicolon, or one of the keywords that signals a postfix expression-statement modifier.  If flags
               includes "PARSE_OPTIONAL" then the expression is optional, otherwise it is mandatory.  It is up to the
               caller to ensure that the dynamic parser state ("PL_parser" et al) is correctly set to reflect the
               source of the code to be parsed and the lexical context for the expression.

               The op tree representing the expression is returned.  If an optional expression is absent, a null
               pointer is returned, otherwise the pointer will be non-null.

               If an error occurs in parsing or compilation, in most cases a valid op tree is returned anyway.  The
               error is reflected in the parser state, normally resulting in a single exception at the top level of
               parsing which covers all the compilation errors that occurred.  Some compilation errors, however, will
               throw an exception immediately.

               NOTE: this function is experimental and may change or be removed without notice.

                       OP *    parse_fullexpr(U32 flags)

       parse_fullstmt
               Parse a single complete Perl statement.  This may be a normal imperative statement or a declaration
               that has compile-time effect, and may include optional labels.  It is up to the caller to ensure that
               the dynamic parser state ("PL_parser" et al) is correctly set to reflect the source of the code to be
               The flags parameter is reserved for future use, and must always be zero.

               NOTE: this function is experimental and may change or be removed without notice.

                       OP *    parse_fullstmt(U32 flags)

       parse_label
               Parse a single label, possibly optional, of the type that may prefix a Perl statement.  It is up to
               the caller to ensure that the dynamic parser state ("PL_parser" et al) is correctly set to reflect the
               source of the code to be parsed.  If flags includes "PARSE_OPTIONAL" then the label is optional,
               otherwise it is mandatory.

               The name of the label is returned in the form of a fresh scalar.  If an optional label is absent, a
               null pointer is returned.

               If an error occurs in parsing, which can only occur if the label is mandatory, a valid label is
               returned anyway.  The error is reflected in the parser state, normally resulting in a single exception
               at the top level of parsing which covers all the compilation errors that occurred.

               NOTE: this function is experimental and may change or be removed without notice.

                       SV *    parse_label(U32 flags)

       parse_listexpr
               Parse a Perl list expression.  This may contain operators of precedence down to the comma operator.
               The expression must be followed (and thus terminated) either by a low-precedence logic operator such
               as "or" or by something that would normally terminate an expression such as semicolon.  If flags
               includes "PARSE_OPTIONAL" then the expression is optional, otherwise it is mandatory.  It is up to the
               caller to ensure that the dynamic parser state ("PL_parser" et al) is correctly set to reflect the
               source of the code to be parsed and the lexical context for the expression.

               The op tree representing the expression is returned.  If an optional expression is absent, a null
               pointer is returned, otherwise the pointer will be non-null.

               If an error occurs in parsing or compilation, in most cases a valid op tree is returned anyway.  The
               error is reflected in the parser state, normally resulting in a single exception at the top level of
               parsing which covers all the compilation errors that occurred.  Some compilation errors, however, will
               throw an exception immediately.

               NOTE: this function is experimental and may change or be removed without notice.

                       OP *    parse_listexpr(U32 flags)

       parse_stmtseq
               Parse a sequence of zero or more Perl statements.  These may be normal imperative statements,
               including optional labels, or declarations that have compile-time effect, or any mixture thereof.  The
               statement sequence ends when a closing brace or end-of-file is encountered in a place where a new
               statement could have validly started.  It is up to the caller to ensure that the dynamic parser state
               ("PL_parser" et al) is correctly set to reflect the source of the code to be parsed and the lexical
               context for the statements.

               The op tree representing the statement sequence is returned.  This may be a null pointer if the
               statements were all null, for example if there were no statements or if there were only subroutine
               definitions (which have compile-time side effects).  If not null, it will be a "lineseq" list,

       parse_termexpr
               Parse a Perl term expression.  This may contain operators of precedence down to the assignment
               operators.  The expression must be followed (and thus terminated) either by a comma or lower-
               precedence operator or by something that would normally terminate an expression such as semicolon.  If
               flags includes "PARSE_OPTIONAL" then the expression is optional, otherwise it is mandatory.  It is up
               to the caller to ensure that the dynamic parser state ("PL_parser" et al) is correctly set to reflect
               the source of the code to be parsed and the lexical context for the expression.

               The op tree representing the expression is returned.  If an optional expression is absent, a null
               pointer is returned, otherwise the pointer will be non-null.

               If an error occurs in parsing or compilation, in most cases a valid op tree is returned anyway.  The
               error is reflected in the parser state, normally resulting in a single exception at the top level of
               parsing which covers all the compilation errors that occurred.  Some compilation errors, however, will
               throw an exception immediately.

               NOTE: this function is experimental and may change or be removed without notice.

                       OP *    parse_termexpr(U32 flags)

       PL_parser
               Pointer to a structure encapsulating the state of the parsing operation currently in progress.  The
               pointer can be locally changed to perform a nested parse without interfering with the state of an
               outer parse.  Individual members of "PL_parser" have their own documentation.

       PL_parser->bufend
               Direct pointer to the end of the chunk of text currently being lexed, the end of the lexer buffer.
               This is equal to "SvPVX(PL_parser->linestr) + SvCUR(PL_parser->linestr)".  A NUL character (zero
               octet) is always located at the end of the buffer, and does not count as part of the buffer's
               contents.

               NOTE: this function is experimental and may change or be removed without notice.

       PL_parser->bufptr
               Points to the current position of lexing inside the lexer buffer.  Characters around this point may be
               freely examined, within the range delimited by "SvPVX("PL_parser->linestr")" and "PL_parser->bufend".
               The octets of the buffer may be intended to be interpreted as either UTF-8 or Latin-1, as indicated by
               "lex_bufutf8".

               Lexing code (whether in the Perl core or not) moves this pointer past the characters that it consumes.
               It is also expected to perform some bookkeeping whenever a newline character is consumed.  This
               movement can be more conveniently performed by the function "lex_read_to", which handles newlines
               appropriately.

               Interpretation of the buffer's octets can be abstracted out by using the slightly higher-level
               functions "lex_peek_unichar" and "lex_read_unichar".

               NOTE: this function is experimental and may change or be removed without notice.

       PL_parser->linestart
               Points to the start of the current line inside the lexer buffer.  This is useful for indicating at
               which column an error occurred, and not much else.  This must be updated by any lexing code that
               consumes a newline; the function "lex_read_to" handles this detail.

               The content of the text chunk in the buffer is commonly exactly one complete line of input, up to and
               including a newline terminator, but there are situations where it is otherwise.  The octets of the
               buffer may be intended to be interpreted as either UTF-8 or Latin-1.  The function "lex_bufutf8" tells
               you which.  Do not use the "SvUTF8" flag on this scalar, which may disagree with it.

               For direct examination of the buffer, the variable "PL_parser->bufend" points to the end of the
               buffer.  The current lexing position is pointed to by "PL_parser->bufptr".  Direct use of these
               pointers is usually preferable to examination of the scalar through normal scalar means.

               NOTE: this function is experimental and may change or be removed without notice.

Magical Functions
       mg_clear
               Clear something magical that the SV represents.  See "sv_magic".

                       int     mg_clear(SV* sv)

       mg_copy Copies the magic from one SV to another.  See "sv_magic".

                       int     mg_copy(SV *sv, SV *nsv, const char *key,
                                       I32 klen)

       mg_find Finds the magic pointer for type matching the SV.  See "sv_magic".

                       MAGIC*  mg_find(const SV* sv, int type)

       mg_findext
               Finds the magic pointer of "type" with the given "vtbl" for the "SV".  See "sv_magicext".

                       MAGIC*  mg_findext(const SV* sv, int type,
                                          const MGVTBL *vtbl)

       mg_free Free any magic storage used by the SV.  See "sv_magic".

                       int     mg_free(SV* sv)

       mg_free_type
               Remove any magic of type how from the SV sv.  See "sv_magic".

                       void    mg_free_type(SV *sv, int how)

       mg_get  Do magic before a value is retrieved from the SV.  See "sv_magic".

                       int     mg_get(SV* sv)

       mg_length
               Report on the SV's length.  See "sv_magic".

                       U32     mg_length(SV* sv)

       mg_magical
               Turns on the magical status of an SV.  See "sv_magic".


                       void    SvLOCK(SV* sv)

       SvSETMAGIC
               Invokes "mg_set" on an SV if it has 'set' magic.  This macro evaluates its argument more than once.

                       void    SvSETMAGIC(SV* sv)

       SvSetMagicSV
               Like "SvSetSV", but does any set magic required afterwards.

                       void    SvSetMagicSV(SV* dsb, SV* ssv)

       SvSetMagicSV_nosteal
               Like "SvSetSV_nosteal", but does any set magic required afterwards.

                       void    SvSetMagicSV_nosteal(SV* dsv, SV* ssv)

       SvSetSV Calls "sv_setsv" if dsv is not the same as ssv.  May evaluate arguments more than once.

                       void    SvSetSV(SV* dsb, SV* ssv)

       SvSetSV_nosteal
               Calls a non-destructive version of "sv_setsv" if dsv is not the same as ssv.  May evaluate arguments
               more than once.

                       void    SvSetSV_nosteal(SV* dsv, SV* ssv)

       SvSHARE Arranges for sv to be shared between threads if a suitable module has been loaded.

                       void    SvSHARE(SV* sv)

       SvUNLOCK
               Releases a mutual exclusion lock on sv if a suitable module has been loaded.

                       void    SvUNLOCK(SV* sv)

Memory Management
       Copy    The XSUB-writer's interface to the C "memcpy" function.  The "src" is the source, "dest" is the
               destination, "nitems" is the number of items, and "type" is the type.  May fail on overlapping copies.
               See also "Move".

                       void    Copy(void* src, void* dest, int nitems, type)

       CopyD   Like "Copy" but returns dest. Useful for encouraging compilers to tail-call optimise.

                       void *  CopyD(void* src, void* dest, int nitems, type)

       Move    The XSUB-writer's interface to the C "memmove" function.  The "src" is the source, "dest" is the
               destination, "nitems" is the number of items, and "type" is the type.  Can do overlapping moves.  See
               also "Copy".

                       void    Move(void* src, void* dest, int nitems, type)


       Newxc   The XSUB-writer's interface to the C "malloc" function, with cast.  See also "Newx".

                       void    Newxc(void* ptr, int nitems, type, cast)

       Newxz   The XSUB-writer's interface to the C "malloc" function.  The allocated memory is zeroed with
               "memzero".  See also "Newx".

                       void    Newxz(void* ptr, int nitems, type)

       Poison  PoisonWith(0xEF) for catching access to freed memory.

                       void    Poison(void* dest, int nitems, type)

       PoisonFree
               PoisonWith(0xEF) for catching access to freed memory.

                       void    PoisonFree(void* dest, int nitems, type)

       PoisonNew
               PoisonWith(0xAB) for catching access to allocated but uninitialized memory.

                       void    PoisonNew(void* dest, int nitems, type)

       PoisonWith
               Fill up memory with a byte pattern (a byte repeated over and over again) that hopefully catches
               attempts to access uninitialized memory.

                       void    PoisonWith(void* dest, int nitems, type,
                                          U8 byte)

       Renew   The XSUB-writer's interface to the C "realloc" function.

                       void    Renew(void* ptr, int nitems, type)

       Renewc  The XSUB-writer's interface to the C "realloc" function, with cast.

                       void    Renewc(void* ptr, int nitems, type, cast)

       Safefree
               The XSUB-writer's interface to the C "free" function.

                       void    Safefree(void* ptr)

       savepv  Perl's version of "strdup()". Returns a pointer to a newly allocated string which is a duplicate of
               "pv". The size of the string is determined by "strlen()". The memory allocated for the new string can
               be freed with the "Safefree()" function.

                       char*   savepv(const char* pv)

       savepvn Perl's version of what "strndup()" would be if it existed. Returns a pointer to a newly allocated
               string which is a duplicate of the first "len" bytes from "pv", plus a trailing NUL byte. The memory
               allocated for the new string can be freed with the "Safefree()" function.


       savesharedpvn
               A version of "savepvn()" which allocates the duplicate string in memory which is shared between
               threads. (With the specific difference that a NULL pointer is not acceptable)

                       char*   savesharedpvn(const char *const pv,
                                             const STRLEN len)

       savesharedpvs
               A version of "savepvs()" which allocates the duplicate string in memory which is shared between
               threads.

                       char*   savesharedpvs(const char* s)

       savesharedsvpv
               A version of "savesharedpv()" which allocates the duplicate string in memory which is shared between
               threads.

                       char*   savesharedsvpv(SV *sv)

       savesvpv
               A version of "savepv()"/"savepvn()" which gets the string to duplicate from the passed in SV using
               "SvPV()"

                       char*   savesvpv(SV* sv)

       StructCopy
               This is an architecture-independent macro to copy one structure to another.

                       void    StructCopy(type src, type dest, type)

       Zero    The XSUB-writer's interface to the C "memzero" function.  The "dest" is the destination, "nitems" is
               the number of items, and "type" is the type.

                       void    Zero(void* dest, int nitems, type)

       ZeroD   Like "Zero" but returns dest. Useful for encouraging compilers to tail-call optimise.

                       void *  ZeroD(void* dest, int nitems, type)

Miscellaneous Functions
       fbm_compile
               Analyses the string in order to make fast searches on it using fbm_instr() -- the Boyer-Moore
               algorithm.

                       void    fbm_compile(SV* sv, U32 flags)

       fbm_instr
               Returns the location of the SV in the string delimited by "str" and "strend".  It returns "NULL" if
               the string can't be found.  The "sv" does not have to be fbm_compiled, but the search will not be as
               fast then.

                       char*   fbm_instr(unsigned char* big,
                                         unsigned char* bigend, SV* littlestr,
                                         U32 flags)

                                             I32 len)

       form    Takes a sprintf-style format pattern and conventional (non-SV) arguments and returns the formatted
               string.

                   (char *) Perl_form(pTHX_ const char* pat, ...)

               can be used any place a string (char *) is required:

                   char * s = Perl_form("%d.%d",major,minor);

               Uses a single private buffer so if you want to format several strings you must explicitly copy the
               earlier strings away (and free the copies when you are done).

                       char*   form(const char* pat, ...)

       getcwd_sv
               Fill the sv with current working directory

                       int     getcwd_sv(SV* sv)

       mess    Take a sprintf-style format pattern and argument list.  These are used to generate a string message.
               If the message does not end with a newline, then it will be extended with some indication of the
               current location in the code, as described for "mess_sv".

               Normally, the resulting message is returned in a new mortal SV.  During global destruction a single SV
               may be shared between uses of this function.

                       SV *    mess(const char *pat, ...)

       mess_sv Expands a message, intended for the user, to include an indication of the current location in the
               code, if the message does not already appear to be complete.

               "basemsg" is the initial message or object.  If it is a reference, it will be used as-is and will be
               the result of this function.  Otherwise it is used as a string, and if it already ends with a newline,
               it is taken to be complete, and the result of this function will be the same string.  If the message
               does not end with a newline, then a segment such as "at foo.pl line 37" will be appended, and possibly
               other clauses indicating the current state of execution.  The resulting message will end with a dot
               and a newline.

               Normally, the resulting message is returned in a new mortal SV.  During global destruction a single SV
               may be shared between uses of this function.  If "consume" is true, then the function is permitted
               (but not required) to modify and return "basemsg" instead of allocating a new SV.

                       SV *    mess_sv(SV *basemsg, bool consume)

       my_snprintf
               The C library "snprintf" functionality, if available and standards-compliant (uses "vsnprintf",
               actually).  However, if the "vsnprintf" is not available, will unfortunately use the unsafe "vsprintf"
               which can overrun the buffer (there is an overrun check, but that may be too late).  Consider using
               "sv_vcatpvf" instead, or getting "vsnprintf".

                       int     my_snprintf(char *buffer, const Size_t len,
                                           const char *format, ...)

               "vsnprintf".

                       int     my_vsnprintf(char *buffer, const Size_t len,
                                            const char *format, va_list ap)

       new_version
               Returns a new version object based on the passed in SV:

                   SV *sv = new_version(SV *ver);

               Does not alter the passed in ver SV.  See "upg_version" if you want to upgrade the SV.

                       SV*     new_version(SV *ver)

       prescan_version
               Validate that a given string can be parsed as a version object, but doesn't actually perform the
               parsing.  Can use either strict or lax validation rules.  Can optionally set a number of hint
               variables to save the parsing code some time when tokenizing.

                       const char* prescan_version(const char *s, bool strict,
                                                   const char** errstr,
                                                   bool *sqv,
                                                   int *ssaw_decimal,
                                                   int *swidth, bool *salpha)

       scan_version
               Returns a pointer to the next character after the parsed version string, as well as upgrading the
               passed in SV to an RV.

               Function must be called with an already existing SV like

                   sv = newSV(0);
                   s = scan_version(s, SV *sv, bool qv);

               Performs some preprocessing to the string to ensure that it has the correct characteristics of a
               version.  Flags the object if it contains an underscore (which denotes this is an alpha version).  The
               boolean qv denotes that the version should be interpreted as if it had multiple decimals, even if it
               doesn't.

                       const char* scan_version(const char *s, SV *rv, bool qv)

       strEQ   Test two strings to see if they are equal.  Returns true or false.

                       bool    strEQ(char* s1, char* s2)

       strGE   Test two strings to see if the first, "s1", is greater than or equal to the second, "s2".  Returns
               true or false.

                       bool    strGE(char* s1, char* s2)

       strGT   Test two strings to see if the first, "s1", is greater than the second, "s2".  Returns true or false.

                       bool    strGT(char* s1, char* s2)


       strnEQ  Test two strings to see if they are equal.  The "len" parameter indicates the number of bytes to
               compare.  Returns true or false. (A wrapper for "strncmp").

                       bool    strnEQ(char* s1, char* s2, STRLEN len)

       strnNE  Test two strings to see if they are different.  The "len" parameter indicates the number of bytes to
               compare.  Returns true or false. (A wrapper for "strncmp").

                       bool    strnNE(char* s1, char* s2, STRLEN len)

       sv_destroyable
               Dummy routine which reports that object can be destroyed when there is no sharing module present.  It
               ignores its single SV argument, and returns 'true'.  Exists to avoid test for a NULL function pointer
               and because it could potentially warn under some level of strict-ness.

                       bool    sv_destroyable(SV *sv)

       sv_nosharing
               Dummy routine which "shares" an SV when there is no sharing module present.  Or "locks" it. Or
               "unlocks" it. In other words, ignores its single SV argument.  Exists to avoid test for a NULL
               function pointer and because it could potentially warn under some level of strict-ness.

                       void    sv_nosharing(SV *sv)

       upg_version
               In-place upgrade of the supplied SV to a version object.

                   SV *sv = upg_version(SV *sv, bool qv);

               Returns a pointer to the upgraded SV.  Set the boolean qv if you want to force this SV to be
               interpreted as an "extended" version.

                       SV*     upg_version(SV *ver, bool qv)

       vcmp    Version object aware cmp.  Both operands must already have been converted into version objects.

                       int     vcmp(SV *lhv, SV *rhv)

       vmess   "pat" and "args" are a sprintf-style format pattern and encapsulated argument list.  These are used to
               generate a string message.  If the message does not end with a newline, then it will be extended with
               some indication of the current location in the code, as described for "mess_sv".

               Normally, the resulting message is returned in a new mortal SV.  During global destruction a single SV
               may be shared between uses of this function.

                       SV *    vmess(const char *pat, va_list *args)

       vnormal Accepts a version object and returns the normalized string representation.  Call like:

                   sv = vnormal(rv);

               NOTE: you can pass either the object directly or the SV contained within the RV.


                       SV*     vnumify(SV *vs)

       vstringify
               In order to maintain maximum compatibility with earlier versions of Perl, this function will return
               either the floating point notation or the multiple dotted notation, depending on whether the original
               version contained 1 or more dots, respectively.

               The SV returned has a refcount of 1.

                       SV*     vstringify(SV *vs)

       vverify Validates that the SV contains valid internal structure for a version object.  It may be passed either
               the version object (RV) or the hash itself (HV).  If the structure is valid, it returns the HV.  If
               the structure is invalid, it returns NULL.

                   SV *hv = vverify(sv);

               Note that it only confirms the bare minimum structure (so as not to get confused by derived classes
               which may contain additional hash entries):

                       SV*     vverify(SV *vs)

MRO Functions
       mro_get_linear_isa
               Returns the mro linearisation for the given stash.  By default, this will be whatever
               "mro_get_linear_isa_dfs" returns unless some other MRO is in effect for the stash.  The return value
               is a read-only AV*.

               You are responsible for "SvREFCNT_inc()" on the return value if you plan to store it anywhere semi-
               permanently (otherwise it might be deleted out from under you the next time the cache is invalidated).

                       AV*     mro_get_linear_isa(HV* stash)

       mro_method_changed_in
               Invalidates method caching on any child classes of the given stash, so that they might notice the
               changes in this one.

               Ideally, all instances of "PL_sub_generation++" in perl source outside of mro.c should be replaced by
               calls to this.

               Perl automatically handles most of the common ways a method might be redefined.  However, there are a
               few ways you could change a method in a stash without the cache code noticing, in which case you need
               to call this method afterwards:

               1) Directly manipulating the stash HV entries from XS code.

               2) Assigning a reference to a readonly scalar constant into a stash entry in order to create a
               constant subroutine (like constant.pm does).

               This same method is available from pure perl via, "mro::method_changed_in(classname)".

                       void    mro_method_changed_in(HV* stash)

       mro_register

                               MULTICALL;

       POP_MULTICALL
               Closing bracket for a lightweight callback.  See "LIGHTWEIGHT CALLBACKS" in perlcall.

                               POP_MULTICALL;

       PUSH_MULTICALL
               Opening bracket for a lightweight callback.  See "LIGHTWEIGHT CALLBACKS" in perlcall.

                               PUSH_MULTICALL;

Numeric functions
       grok_bin
               converts a string representing a binary number to numeric form.

               On entry start and *len give the string to scan, *flags gives conversion flags, and result should be
               NULL or a pointer to an NV.  The scan stops at the end of the string, or the first invalid character.
               Unless "PERL_SCAN_SILENT_ILLDIGIT" is set in *flags, encountering an invalid character will also
               trigger a warning.  On return *len is set to the length of the scanned string, and *flags gives output
               flags.

               If the value is <= "UV_MAX" it is returned as a UV, the output flags are clear, and nothing is written
               to *result. If the value is > UV_MAX "grok_bin" returns UV_MAX, sets "PERL_SCAN_GREATER_THAN_UV_MAX"
               in the output flags, and writes the value to *result (or the value is discarded if result is NULL).

               The binary number may optionally be prefixed with "0b" or "b" unless "PERL_SCAN_DISALLOW_PREFIX" is
               set in *flags on entry. If "PERL_SCAN_ALLOW_UNDERSCORES" is set in *flags then the binary number may
               use '_' characters to separate digits.

                       UV      grok_bin(const char* start, STRLEN* len_p,
                                        I32* flags, NV *result)

       grok_hex
               converts a string representing a hex number to numeric form.

               On entry start and *len give the string to scan, *flags gives conversion flags, and result should be
               NULL or a pointer to an NV.  The scan stops at the end of the string, or the first invalid character.
               Unless "PERL_SCAN_SILENT_ILLDIGIT" is set in *flags, encountering an invalid character will also
               trigger a warning.  On return *len is set to the length of the scanned string, and *flags gives output
               flags.

               If the value is <= UV_MAX it is returned as a UV, the output flags are clear, and nothing is written
               to *result. If the value is > UV_MAX "grok_hex" returns UV_MAX, sets "PERL_SCAN_GREATER_THAN_UV_MAX"
               in the output flags, and writes the value to *result (or the value is discarded if result is NULL).

               The hex number may optionally be prefixed with "0x" or "x" unless "PERL_SCAN_DISALLOW_PREFIX" is set
               in *flags on entry. If "PERL_SCAN_ALLOW_UNDERSCORES" is set in *flags then the hex number may use '_'
               characters to separate digits.

                       UV      grok_hex(const char* start, STRLEN* len_p,
                                        I32* flags, NV *result)


               *valuep gives the true value truncated to an integer), and IS_NUMBER_NEG if the number is negative (in
               which case *valuep holds the absolute value).  IS_NUMBER_IN_UV is not set if e notation was used or
               the number is larger than a UV.

                       int     grok_number(const char *pv, STRLEN len,
                                           UV *valuep)

       grok_numeric_radix
               Scan and skip for a numeric decimal separator (radix).

                       bool    grok_numeric_radix(const char **sp,
                                                  const char *send)

       grok_oct
               converts a string representing an octal number to numeric form.

               On entry start and *len give the string to scan, *flags gives conversion flags, and result should be
               NULL or a pointer to an NV.  The scan stops at the end of the string, or the first invalid character.
               Unless "PERL_SCAN_SILENT_ILLDIGIT" is set in *flags, encountering an 8 or 9 will also trigger a
               warning.  On return *len is set to the length of the scanned string, and *flags gives output flags.

               If the value is <= UV_MAX it is returned as a UV, the output flags are clear, and nothing is written
               to *result. If the value is > UV_MAX "grok_oct" returns UV_MAX, sets "PERL_SCAN_GREATER_THAN_UV_MAX"
               in the output flags, and writes the value to *result (or the value is discarded if result is NULL).

               If "PERL_SCAN_ALLOW_UNDERSCORES" is set in *flags then the octal number may use '_' characters to
               separate digits.

                       UV      grok_oct(const char* start, STRLEN* len_p,
                                        I32* flags, NV *result)

       Perl_signbit
               Return a non-zero integer if the sign bit on an NV is set, and 0 if it is not.

               If Configure detects this system has a signbit() that will work with our NVs, then we just use it via
               the #define in perl.h.  Otherwise, fall back on this implementation.  As a first pass, this gets
               everything right except -0.0.  Alas, catching -0.0 is the main use for this function, so this is not
               too helpful yet.  Still, at least we have the scaffolding in place to support other systems, should
               that prove useful.

               Configure notes:  This function is called 'Perl_signbit' instead of a plain 'signbit' because it is
               easy to imagine a system having a signbit() function or macro that doesn't happen to work with our
               particular choice of NVs.  We shouldn't just re-#define signbit as Perl_signbit and expect the
               standard system headers to be happy.  Also, this is a no-context function (no pTHX_) because
               Perl_signbit() is usually re-#defined in perl.h as a simple macro call to the system's signbit().
               Users should just always call Perl_signbit().

               NOTE: this function is experimental and may change or be removed without notice.

                       int     Perl_signbit(NV f)

       scan_bin
               For backwards compatibility. Use "grok_bin" instead.


                       NV      scan_oct(const char* start, STRLEN len,
                                        STRLEN* retlen)

Optree construction
       newASSIGNOP
               Constructs, checks, and returns an assignment op.  left and right supply the parameters of the
               assignment; they are consumed by this function and become part of the constructed op tree.

               If optype is "OP_ANDASSIGN", "OP_ORASSIGN", or "OP_DORASSIGN", then a suitable conditional optree is
               constructed.  If optype is the opcode of a binary operator, such as "OP_BIT_OR", then an op is
               constructed that performs the binary operation and assigns the result to the left argument.  Either
               way, if optype is non-zero then flags has no effect.

               If optype is zero, then a plain scalar or list assignment is constructed.  Which type of assignment it
               is is automatically determined.  flags gives the eight bits of "op_flags", except that "OPf_KIDS" will
               be set automatically, and, shifted up eight bits, the eight bits of "op_private", except that the bit
               with value 1 or 2 is automatically set as required.

                       OP *    newASSIGNOP(I32 flags, OP *left, I32 optype,
                                           OP *right)

       newBINOP
               Constructs, checks, and returns an op of any binary type.  type is the opcode.  flags gives the eight
               bits of "op_flags", except that "OPf_KIDS" will be set automatically, and, shifted up eight bits, the
               eight bits of "op_private", except that the bit with value 1 or 2 is automatically set as required.
               first and last supply up to two ops to be the direct children of the binary op; they are consumed by
               this function and become part of the constructed op tree.

                       OP *    newBINOP(I32 type, I32 flags, OP *first,
                                        OP *last)

       newCONDOP
               Constructs, checks, and returns a conditional-expression ("cond_expr") op.  flags gives the eight bits
               of "op_flags", except that "OPf_KIDS" will be set automatically, and, shifted up eight bits, the eight
               bits of "op_private", except that the bit with value 1 is automatically set.  first supplies the
               expression selecting between the two branches, and trueop and falseop supply the branches; they are
               consumed by this function and become part of the constructed op tree.

                       OP *    newCONDOP(I32 flags, OP *first, OP *trueop,
                                         OP *falseop)

       newFOROP
               Constructs, checks, and returns an op tree expressing a "foreach" loop (iteration through a list of
               values).  This is a heavyweight loop, with structure that allows exiting the loop by "last" and
               suchlike.

               sv optionally supplies the variable that will be aliased to each item in turn; if null, it defaults to
               $_ (either lexical or global).  expr supplies the list of values to iterate over.  block supplies the
               main body of the loop, and cont optionally supplies a "continue" block that operates as a second half
               of the body.  All of these optree inputs are consumed by this function and become part of the
               constructed op tree.

               flags gives the eight bits of "op_flags" for the "leaveloop" op and, shifted up eight bits, the eight
               bits of "op_private" for the "leaveloop" op, except that (in both cases) some bits will be set

                                          PADOFFSET defsv_off)

       newGVOP Constructs, checks, and returns an op of any type that involves an embedded reference to a GV.  type
               is the opcode.  flags gives the eight bits of "op_flags".  gv identifies the GV that the op should
               reference; calling this function does not transfer ownership of any reference to it.

                       OP *    newGVOP(I32 type, I32 flags, GV *gv)

       newLISTOP
               Constructs, checks, and returns an op of any list type.  type is the opcode.  flags gives the eight
               bits of "op_flags", except that "OPf_KIDS" will be set automatically if required.  first and last
               supply up to two ops to be direct children of the list op; they are consumed by this function and
               become part of the constructed op tree.

                       OP *    newLISTOP(I32 type, I32 flags, OP *first,
                                         OP *last)

       newLOGOP
               Constructs, checks, and returns a logical (flow control) op.  type is the opcode.  flags gives the
               eight bits of "op_flags", except that "OPf_KIDS" will be set automatically, and, shifted up eight
               bits, the eight bits of "op_private", except that the bit with value 1 is automatically set.  first
               supplies the expression controlling the flow, and other supplies the side (alternate) chain of ops;
               they are consumed by this function and become part of the constructed op tree.

                       OP *    newLOGOP(I32 type, I32 flags, OP *first,
                                        OP *other)

       newLOOPEX
               Constructs, checks, and returns a loop-exiting op (such as "goto" or "last").  type is the opcode.
               label supplies the parameter determining the target of the op; it is consumed by this function and
               become part of the constructed op tree.

                       OP *    newLOOPEX(I32 type, OP *label)

       newLOOPOP
               Constructs, checks, and returns an op tree expressing a loop.  This is only a loop in the control flow
               through the op tree; it does not have the heavyweight loop structure that allows exiting the loop by
               "last" and suchlike.  flags gives the eight bits of "op_flags" for the top-level op, except that some
               bits will be set automatically as required.  expr supplies the expression controlling loop iteration,
               and block supplies the body of the loop; they are consumed by this function and become part of the
               constructed op tree.  debuggable is currently unused and should always be 1.

                       OP *    newLOOPOP(I32 flags, I32 debuggable, OP *expr,
                                         OP *block)

       newNULLLIST
               Constructs, checks, and returns a new "stub" op, which represents an empty list expression.

                       OP *    newNULLLIST()

       newOP   Constructs, checks, and returns an op of any base type (any type that has no extra fields).  type is
               the opcode.  flags gives the eight bits of "op_flags", and, shifted up eight bits, the eight bits of
               "op_private".

               the eight bits of "op_flags" and, shifted up eight bits, the eight bits of "op_private".

                       OP *    newPMOP(I32 type, I32 flags)

       newPVOP Constructs, checks, and returns an op of any type that involves an embedded C-level pointer (PV).
               type is the opcode.  flags gives the eight bits of "op_flags".  pv supplies the C-level pointer, which
               must have been allocated using "PerlMemShared_malloc"; the memory will be freed when the op is
               destroyed.

                       OP *    newPVOP(I32 type, I32 flags, char *pv)

       newRANGE
               Constructs and returns a "range" op, with subordinate "flip" and "flop" ops.  flags gives the eight
               bits of "op_flags" for the "flip" op and, shifted up eight bits, the eight bits of "op_private" for
               both the "flip" and "range" ops, except that the bit with value 1 is automatically set.  left and
               right supply the expressions controlling the endpoints of the range; they are consumed by this
               function and become part of the constructed op tree.

                       OP *    newRANGE(I32 flags, OP *left, OP *right)

       newSLICEOP
               Constructs, checks, and returns an "lslice" (list slice) op.  flags gives the eight bits of
               "op_flags", except that "OPf_KIDS" will be set automatically, and, shifted up eight bits, the eight
               bits of "op_private", except that the bit with value 1 or 2 is automatically set as required.  listval
               and subscript supply the parameters of the slice; they are consumed by this function and become part
               of the constructed op tree.

                       OP *    newSLICEOP(I32 flags, OP *subscript,
                                          OP *listval)

       newSTATEOP
               Constructs a state op (COP).  The state op is normally a "nextstate" op, but will be a "dbstate" op if
               debugging is enabled for currently-compiled code.  The state op is populated from "PL_curcop" (or
               "PL_compiling").  If label is non-null, it supplies the name of a label to attach to the state op;
               this function takes ownership of the memory pointed at by label, and will free it.  flags gives the
               eight bits of "op_flags" for the state op.

               If o is null, the state op is returned.  Otherwise the state op is combined with o into a "lineseq"
               list op, which is returned.  o is consumed by this function and becomes part of the returned op tree.

                       OP *    newSTATEOP(I32 flags, char *label, OP *o)

       newSVOP Constructs, checks, and returns an op of any type that involves an embedded SV.  type is the opcode.
               flags gives the eight bits of "op_flags".  sv gives the SV to embed in the op; this function takes
               ownership of one reference to it.

                       OP *    newSVOP(I32 type, I32 flags, SV *sv)

       newUNOP Constructs, checks, and returns an op of any unary type.  type is the opcode.  flags gives the eight
               bits of "op_flags", except that "OPf_KIDS" will be set automatically if required, and, shifted up
               eight bits, the eight bits of "op_private", except that the bit with value 1 is automatically set.
               first supplies an optional op to be the direct child of the unary op; it is consumed by this function
               and become part of the constructed op tree.

               with structure that allows exiting the loop by "last" and suchlike.

               loop is an optional preconstructed "enterloop" op to use in the loop; if it is null then a suitable op
               will be constructed automatically.  expr supplies the loop's controlling expression.  block supplies
               the main body of the loop, and cont optionally supplies a "continue" block that operates as a second
               half of the body.  All of these optree inputs are consumed by this function and become part of the
               constructed op tree.

               flags gives the eight bits of "op_flags" for the "leaveloop" op and, shifted up eight bits, the eight
               bits of "op_private" for the "leaveloop" op, except that (in both cases) some bits will be set
               automatically.  debuggable is currently unused and should always be 1.  has_my can be supplied as true
               to force the loop body to be enclosed in its own scope.

                       OP *    newWHILEOP(I32 flags, I32 debuggable,
                                          LOOP *loop, OP *expr, OP *block,
                                          OP *cont, I32 has_my)

Optree Manipulation Functions
       ck_entersub_args_list
               Performs the default fixup of the arguments part of an "entersub" op tree.  This consists of applying
               list context to each of the argument ops.  This is the standard treatment used on a call marked with
               "&", or a method call, or a call through a subroutine reference, or any other call where the callee
               can't be identified at compile time, or a call where the callee has no prototype.

                       OP *    ck_entersub_args_list(OP *entersubop)

       ck_entersub_args_proto
               Performs the fixup of the arguments part of an "entersub" op tree based on a subroutine prototype.
               This makes various modifications to the argument ops, from applying context up to inserting "refgen"
               ops, and checking the number and syntactic types of arguments, as directed by the prototype.  This is
               the standard treatment used on a subroutine call, not marked with "&", where the callee can be
               identified at compile time and has a prototype.

               protosv supplies the subroutine prototype to be applied to the call.  It may be a normal defined
               scalar, of which the string value will be used.  Alternatively, for convenience, it may be a
               subroutine object (a "CV*" that has been cast to "SV*") which has a prototype.  The prototype
               supplied, in whichever form, does not need to match the actual callee referenced by the op tree.

               If the argument ops disagree with the prototype, for example by having an unacceptable number of
               arguments, a valid op tree is returned anyway.  The error is reflected in the parser state, normally
               resulting in a single exception at the top level of parsing which covers all the compilation errors
               that occurred.  In the error message, the callee is referred to by the name defined by the namegv
               parameter.

                       OP *    ck_entersub_args_proto(OP *entersubop,
                                                      GV *namegv, SV *protosv)

       ck_entersub_args_proto_or_list
               Performs the fixup of the arguments part of an "entersub" op tree either based on a subroutine
               prototype or using default list-context processing.  This is the standard treatment used on a
               subroutine call, not marked with "&", where the callee can be identified at compile time.

               protosv supplies the subroutine prototype to be applied to the call, or indicates that there is no
               prototype.  It may be a normal scalar, in which case if it is defined then the string value will be

                                                              GV *namegv,
                                                              SV *protosv)

       cv_const_sv
               If "cv" is a constant sub eligible for inlining. returns the constant value returned by the sub.
               Otherwise, returns NULL.

               Constant subs can be created with "newCONSTSUB" or as described in "Constant Functions" in perlsub.

                       SV*     cv_const_sv(const CV *const cv)

       cv_get_call_checker
               Retrieves the function that will be used to fix up a call to cv.  Specifically, the function is
               applied to an "entersub" op tree for a subroutine call, not marked with "&", where the callee can be
               identified at compile time as cv.

               The C-level function pointer is returned in *ckfun_p, and an SV argument for it is returned in
               *ckobj_p.  The function is intended to be called in this manner:

                   entersubop = (*ckfun_p)(aTHX_ entersubop, namegv, (*ckobj_p));

               In this call, entersubop is a pointer to the "entersub" op, which may be replaced by the check
               function, and namegv is a GV supplying the name that should be used by the check function to refer to
               the callee of the "entersub" op if it needs to emit any diagnostics.  It is permitted to apply the
               check function in non-standard situations, such as to a call to a different subroutine or to a method
               call.

               By default, the function is Perl_ck_entersub_args_proto_or_list, and the SV parameter is cv itself.
               This implements standard prototype processing.  It can be changed, for a particular subroutine, by
               "cv_set_call_checker".

                       void    cv_get_call_checker(CV *cv,
                                                   Perl_call_checker *ckfun_p,
                                                   SV **ckobj_p)

       cv_set_call_checker
               Sets the function that will be used to fix up a call to cv.  Specifically, the function is applied to
               an "entersub" op tree for a subroutine call, not marked with "&", where the callee can be identified
               at compile time as cv.

               The C-level function pointer is supplied in ckfun, and an SV argument for it is supplied in ckobj.
               The function is intended to be called in this manner:

                   entersubop = ckfun(aTHX_ entersubop, namegv, ckobj);

               In this call, entersubop is a pointer to the "entersub" op, which may be replaced by the check
               function, and namegv is a GV supplying the name that should be used by the check function to refer to
               the callee of the "entersub" op if it needs to emit any diagnostics.  It is permitted to apply the
               check function in non-standard situations, such as to a call to a different subroutine or to a method
               call.

               The current setting for a particular CV can be retrieved by "cv_get_call_checker".

                       void    cv_set_call_checker(CV *cv,

                       CV*     newCONSTSUB(HV* stash, const char* name, SV* sv)

       newCONSTSUB_flags
               Creates a constant sub equivalent to Perl "sub FOO () { 123 }" which is eligible for inlining at
               compile-time.

               Currently, the only useful value for "flags" is SVf_UTF8.

               Passing NULL for SV creates a constant sub equivalent to "sub BAR () {}", which won't be called if
               used as a destructor, but will suppress the overhead of a call to "AUTOLOAD".  (This form, however,
               isn't eligible for inlining at compile time.)

                       CV*     newCONSTSUB_flags(HV* stash, const char* name,
                                                 STRLEN len, U32 flags, SV* sv)

       newXS   Used by "xsubpp" to hook up XSUBs as Perl subs.  filename needs to be static storage, as it is used
               directly as CvFILE(), without a copy being made.

       op_append_elem
               Append an item to the list of ops contained directly within a list-type op, returning the lengthened
               list.  first is the list-type op, and last is the op to append to the list.  optype specifies the
               intended opcode for the list.  If first is not already a list of the right type, it will be upgraded
               into one.  If either first or last is null, the other is returned unchanged.

                       OP *    op_append_elem(I32 optype, OP *first, OP *last)

       op_append_list
               Concatenate the lists of ops contained directly within two list-type ops, returning the combined list.
               first and last are the list-type ops to concatenate.  optype specifies the intended opcode for the
               list.  If either first or last is not already a list of the right type, it will be upgraded into one.
               If either first or last is null, the other is returned unchanged.

                       OP *    op_append_list(I32 optype, OP *first, OP *last)

       OP_CLASS
               Return the class of the provided OP: that is, which of the *OP structures it uses. For core ops this
               currently gets the information out of PL_opargs, which does not always accurately reflect the type
               used.  For custom ops the type is returned from the registration, and it is up to the registree to
               ensure it is accurate. The value returned will be one of the OA_* constants from op.h.

                       U32     OP_CLASS(OP *o)

       OP_DESC Return a short description of the provided OP.

                       const char * OP_DESC(OP *o)

       op_linklist
               This function is the implementation of the "LINKLIST" macro. It should not be called directly.

                       OP*     op_linklist(OP *o)

       op_lvalue
               Propagate lvalue ("modifiable") context to an op and its children.  type represents the context type,

                       OP *    op_lvalue(OP *o, I32 type)

       OP_NAME Return the name of the provided OP. For core ops this looks up the name from the op_type; for custom
               ops from the op_ppaddr.

                       const char * OP_NAME(OP *o)

       op_prepend_elem
               Prepend an item to the list of ops contained directly within a list-type op, returning the lengthened
               list.  first is the op to prepend to the list, and last is the list-type op.  optype specifies the
               intended opcode for the list.  If last is not already a list of the right type, it will be upgraded
               into one.  If either first or last is null, the other is returned unchanged.

                       OP *    op_prepend_elem(I32 optype, OP *first, OP *last)

       op_scope
               Wraps up an op tree with some additional ops so that at runtime a dynamic scope will be created.  The
               original ops run in the new dynamic scope, and then, provided that they exit normally, the scope will
               be unwound.  The additional ops used to create and unwind the dynamic scope will normally be an
               "enter"/"leave" pair, but a "scope" op may be used instead if the ops are simple enough to not need
               the full dynamic scope structure.

               NOTE: this function is experimental and may change or be removed without notice.

                       OP *    op_scope(OP *o)

       rv2cv_op_cv
               Examines an op, which is expected to identify a subroutine at runtime, and attempts to determine at
               compile time which subroutine it identifies.  This is normally used during Perl compilation to
               determine whether a prototype can be applied to a function call.  cvop is the op being considered,
               normally an "rv2cv" op.  A pointer to the identified subroutine is returned, if it could be determined
               statically, and a null pointer is returned if it was not possible to determine statically.

               Currently, the subroutine can be identified statically if the RV that the "rv2cv" is to operate on is
               provided by a suitable "gv" or "const" op.  A "gv" op is suitable if the GV's CV slot is populated.  A
               "const" op is suitable if the constant value must be an RV pointing to a CV.  Details of this process
               may change in future versions of Perl.  If the "rv2cv" op has the "OPpENTERSUB_AMPER" flag set then no
               attempt is made to identify the subroutine statically: this flag is used to suppress compile-time
               magic on a subroutine call, forcing it to use default runtime behaviour.

               If flags has the bit "RV2CVOPCV_MARK_EARLY" set, then the handling of a GV reference is modified.  If
               a GV was examined and its CV slot was found to be empty, then the "gv" op has the "OPpEARLY_CV" flag
               set.  If the op is not optimised away, and the CV slot is later populated with a subroutine having a
               prototype, that flag eventually triggers the warning "called too early to check prototype".

               If flags has the bit "RV2CVOPCV_RETURN_NAME_GV" set, then instead of returning a pointer to the
               subroutine it returns a pointer to the GV giving the most appropriate name for the subroutine in this
               context.  Normally this is just the "CvGV" of the subroutine, but for an anonymous ("CvANON")
               subroutine that is referenced through a GV it will be the referencing GV.  The resulting "GV*" is cast
               to "CV*" to be returned.  A null pointer is returned as usual if there is no statically-determinable
               subroutine.

                       CV *    rv2cv_op_cv(OP *cvop, U32 flags)


               The CvPADLIST AV has the REFCNT of its component items managed "manually" (mostly in pad.c) rather
               than by normal av.c rules.  So we turn off AvREAL just before freeing it, to let av.c know not to
               touch the entries.  The items in the AV are not SVs as for a normal AV, but other AVs:

               0'th Entry of the CvPADLIST is an AV which represents the "names" or rather the "static type
               information" for lexicals.

               The CvDEPTH'th entry of CvPADLIST AV is an AV which is the stack frame at that depth of recursion into
               the CV.  The 0'th slot of a frame AV is an AV which is @_.  other entries are storage for variables
               and op targets.

               Iterating over the names AV iterates over all possible pad items. Pad slots that are SVs_PADTMP
               (targets/GVs/constants) end up having &PL_sv_undef "names" (see pad_alloc()).

               Only my/our variable (SVs_PADMY/SVs_PADOUR) slots get valid names.  The rest are op
               targets/GVs/constants which are statically allocated or resolved at compile time.  These don't have
               names by which they can be looked up from Perl code at run time through eval"" like my/our variables
               can be.  Since they can't be looked up by "name" but only by their index allocated at compile time
               (which is usually in PL_op->op_targ), wasting a name SV for them doesn't make sense.

               The SVs in the names AV have their PV being the name of the variable.  xlow+1..xhigh inclusive in the
               NV union is a range of cop_seq numbers for which the name is valid (accessed through the macros
               COP_SEQ_RANGE_LOW and _HIGH).  During compilation, these fields may hold the special value
               PERL_PADSEQ_INTRO to indicate various stages:

                  COP_SEQ_RANGE_LOW        _HIGH
                  -----------------        -----
                  PERL_PADSEQ_INTRO            0   variable not yet introduced:   { my ($x
                  valid-seq#   PERL_PADSEQ_INTRO   variable in scope:             { my ($x)
                  valid-seq#          valid-seq#   compilation of scope complete: { my ($x) }

               For typed lexicals name SV is SVt_PVMG and SvSTASH points at the type.  For "our" lexicals, the type
               is also SVt_PVMG, with the SvOURSTASH slot pointing at the stash of the associated global (so that
               duplicate "our" declarations in the same package can be detected).  SvUVX is sometimes hijacked to
               store the generation number during compilation.

               If SvFAKE is set on the name SV, then that slot in the frame AV is a REFCNT'ed reference to a lexical
               from "outside". In this case, the name SV does not use xlow and xhigh to store a cop_seq range, since
               it is in scope throughout. Instead xhigh stores some flags containing info about the real lexical (is
               it declared in an anon, and is it capable of being instantiated multiple times?), and for fake ANONs,
               xlow contains the index within the parent's pad where the lexical's value is stored, to make cloning
               quicker.

               If the 'name' is '&' the corresponding entry in frame AV is a CV representing a possible closure.
               (SvFAKE and name of '&' is not a meaningful combination currently but could become so if "my sub foo
               {}" is implemented.)

               Note that formats are treated as anon subs, and are cloned each time write is called (if necessary).

               The flag SVs_PADSTALE is cleared on lexicals each time the my() is executed, and set on scope exit.
               This allows the 'Variable $x is not available' warning to be generated in evals, such as

                   { my $x = 1; sub f { eval '$x'} } f();


       pad_findmy_pvs
               Exactly like "pad_findmy_pvn", but takes a literal string instead of a string/length pair.

                       PADOFFSET pad_findmy_pvs(const char *name, U32 flags)

       pad_new Create a new padlist, updating the global variables for the currently-compiling padlist to point to
               the new padlist.  The following flags can be OR'ed together:

                   padnew_CLONE        this pad is for a cloned CV
                   padnew_SAVE         save old globals on the save stack
                   padnew_SAVESUB      also save extra stuff for start of sub

                       PADLIST * pad_new(int flags)

       PL_comppad
               During compilation, this points to the array containing the values part of the pad for the currently-
               compiling code.  (At runtime a CV may have many such value arrays; at compile time just one is
               constructed.)  At runtime, this points to the array containing the currently-relevant values for the
               pad for the currently-executing code.

               NOTE: this function is experimental and may change or be removed without notice.

       PL_comppad_name
               During compilation, this points to the array containing the names part of the pad for the currently-
               compiling code.

               NOTE: this function is experimental and may change or be removed without notice.

       PL_curpad
               Points directly to the body of the "PL_comppad" array.  (I.e., this is "AvARRAY(PL_comppad)".)

               NOTE: this function is experimental and may change or be removed without notice.

Per-Interpreter Variables
       PL_modglobal
               "PL_modglobal" is a general purpose, interpreter global HV for use by extensions that need to keep
               information on a per-interpreter basis.  In a pinch, it can also be used as a symbol table for
               extensions to share data among each other.  It is a good idea to use keys prefixed by the package name
               of the extension that owns the data.

                       HV*     PL_modglobal

       PL_na   A convenience variable which is typically used with "SvPV" when one doesn't care about the length of
               the string.  It is usually more efficient to either declare a local variable and use that instead or
               to use the "SvPV_nolen" macro.

                       STRLEN  PL_na

       PL_opfreehook
               When non-"NULL", the function pointed by this variable will be called each time an OP is freed with
               the corresponding OP as the argument.  This allows extensions to free any extra attribute they have
               locally attached to an OP.  It is also assured to first fire for the parent OP and then for its kids.

               When you replace this variable, it is considered a good practice to store the possibly previously
               existing optimiser.  The basic way to do this can be seen in "Compile pass 3: peephole optimization"
               in perlguts.  If the new code wishes to operate on ops throughout the subroutine's structure, rather
               than just at the top level, it is likely to be more convenient to wrap the "PL_rpeepp" hook.

                       peep_t  PL_peepp

       PL_rpeepp
               Pointer to the recursive peephole optimiser.  This is a function that gets called at the end of
               compilation of a Perl subroutine (or equivalently independent piece of Perl code) to perform fixups of
               some ops and to perform small-scale optimisations.  The function is called once for each chain of ops
               linked through their "op_next" fields; it is recursively called to handle each side chain.  It is
               passed, as sole parameter, a pointer to the op that is at the head of the chain.  It modifies the op
               tree in place.

               The peephole optimiser should never be completely replaced.  Rather, add code to it by wrapping the
               existing optimiser.  The basic way to do this can be seen in "Compile pass 3: peephole optimization"
               in perlguts.  If the new code wishes to operate only on ops at a subroutine's top level, rather than
               throughout the structure, it is likely to be more convenient to wrap the "PL_peepp" hook.

                       peep_t  PL_rpeepp

       PL_sv_no
               This is the "false" SV.  See "PL_sv_yes".  Always refer to this as &PL_sv_no.

                       SV      PL_sv_no

       PL_sv_undef
               This is the "undef" SV.  Always refer to this as &PL_sv_undef.

                       SV      PL_sv_undef

       PL_sv_yes
               This is the "true" SV.  See "PL_sv_no".  Always refer to this as &PL_sv_yes.

                       SV      PL_sv_yes

REGEXP Functions
       SvRX    Convenience macro to get the REGEXP from a SV. This is approximately equivalent to the following
               snippet:

                   if (SvMAGICAL(sv))
                       mg_get(sv);
                   if (SvROK(sv))
                       sv = MUTABLE_SV(SvRV(sv));
                   if (SvTYPE(sv) == SVt_REGEXP)
                       return (REGEXP*) sv;

               NULL will be returned if a REGEXP* is not found.

                       REGEXP * SvRX(SV *sv)

       SvRXOK  Returns a boolean indicating whether the SV (or the one it references) is a REGEXP.

               If you want to do something with the REGEXP* later use SvRX instead and check for NULL.
               Rethrows a previously caught exception.  See "Exception Handling" in perlguts.

                               XCPT_RETHROW;

       XCPT_TRY_END
               Ends a try block.  See "Exception Handling" in perlguts.

       XCPT_TRY_START
               Starts a try block.  See "Exception Handling" in perlguts.

Stack Manipulation Macros
       dMARK   Declare a stack marker variable, "mark", for the XSUB.  See "MARK" and "dORIGMARK".

                               dMARK;

       dORIGMARK
               Saves the original stack mark for the XSUB.  See "ORIGMARK".

                               dORIGMARK;

       dSP     Declares a local copy of perl's stack pointer for the XSUB, available via the "SP" macro.  See "SP".

                               dSP;

       EXTEND  Used to extend the argument stack for an XSUB's return values. Once used, guarantees that there is
               room for at least "nitems" to be pushed onto the stack.

                       void    EXTEND(SP, int nitems)

       MARK    Stack marker variable for the XSUB.  See "dMARK".

       mPUSHi  Push an integer onto the stack.  The stack must have room for this element.  Does not use "TARG".  See
               also "PUSHi", "mXPUSHi" and "XPUSHi".

                       void    mPUSHi(IV iv)

       mPUSHn  Push a double onto the stack.  The stack must have room for this element.  Does not use "TARG".  See
               also "PUSHn", "mXPUSHn" and "XPUSHn".

                       void    mPUSHn(NV nv)

       mPUSHp  Push a string onto the stack.  The stack must have room for this element.  The "len" indicates the
               length of the string.  Does not use "TARG".  See also "PUSHp", "mXPUSHp" and "XPUSHp".

                       void    mPUSHp(char* str, STRLEN len)

       mPUSHs  Push an SV onto the stack and mortalizes the SV.  The stack must have room for this element.  Does not
               use "TARG".  See also "PUSHs" and "mXPUSHs".

                       void    mPUSHs(SV* sv)

       mPUSHu  Push an unsigned integer onto the stack.  The stack must have room for this element.  Does not use
               "TARG".  See also "PUSHu", "mXPUSHu" and "XPUSHu".


       mXPUSHp Push a string onto the stack, extending the stack if necessary.  The "len" indicates the length of the
               string.  Does not use "TARG".  See also "XPUSHp", "mPUSHp" and "PUSHp".

                       void    mXPUSHp(char* str, STRLEN len)

       mXPUSHs Push an SV onto the stack, extending the stack if necessary and mortalizes the SV.  Does not use
               "TARG".  See also "XPUSHs" and "mPUSHs".

                       void    mXPUSHs(SV* sv)

       mXPUSHu Push an unsigned integer onto the stack, extending the stack if necessary.  Does not use "TARG".  See
               also "XPUSHu", "mPUSHu" and "PUSHu".

                       void    mXPUSHu(UV uv)

       ORIGMARK
               The original stack mark for the XSUB.  See "dORIGMARK".

       POPi    Pops an integer off the stack.

                       IV      POPi

       POPl    Pops a long off the stack.

                       long    POPl

       POPn    Pops a double off the stack.

                       NV      POPn

       POPp    Pops a string off the stack. Deprecated. New code should use POPpx.

                       char*   POPp

       POPpbytex
               Pops a string off the stack which must consist of bytes i.e. characters < 256.

                       char*   POPpbytex

       POPpx   Pops a string off the stack.

                       char*   POPpx

       POPs    Pops an SV off the stack.

                       SV*     POPs

       PUSHi   Push an integer onto the stack.  The stack must have room for this element.  Handles 'set' magic.
               Uses "TARG", so "dTARGET" or "dXSTARG" should be called to declare it.  Do not call multiple
               "TARG"-oriented macros to return lists from XSUB's - see "mPUSHi" instead.  See also "XPUSHi" and
               "mXPUSHi".

                       void    PUSHi(IV iv)


               "TARG", so "dTARGET" or "dXSTARG" should be called to declare it.  Do not call multiple
               "TARG"-oriented macros to return lists from XSUB's - see "mPUSHn" instead.  See also "XPUSHn" and
               "mXPUSHn".

                       void    PUSHn(NV nv)

       PUSHp   Push a string onto the stack.  The stack must have room for this element.  The "len" indicates the
               length of the string.  Handles 'set' magic.  Uses "TARG", so "dTARGET" or "dXSTARG" should be called
               to declare it.  Do not call multiple "TARG"-oriented macros to return lists from XSUB's - see "mPUSHp"
               instead.  See also "XPUSHp" and "mXPUSHp".

                       void    PUSHp(char* str, STRLEN len)

       PUSHs   Push an SV onto the stack.  The stack must have room for this element.  Does not handle 'set' magic.
               Does not use "TARG".  See also "PUSHmortal", "XPUSHs" and "XPUSHmortal".

                       void    PUSHs(SV* sv)

       PUSHu   Push an unsigned integer onto the stack.  The stack must have room for this element.  Handles 'set'
               magic.  Uses "TARG", so "dTARGET" or "dXSTARG" should be called to declare it.  Do not call multiple
               "TARG"-oriented macros to return lists from XSUB's - see "mPUSHu" instead.  See also "XPUSHu" and
               "mXPUSHu".

                       void    PUSHu(UV uv)

       PUTBACK Closing bracket for XSUB arguments.  This is usually handled by "xsubpp".  See "PUSHMARK" and perlcall
               for other uses.

                               PUTBACK;

       SP      Stack pointer.  This is usually handled by "xsubpp".  See "dSP" and "SPAGAIN".

       SPAGAIN Refetch the stack pointer.  Used after a callback.  See perlcall.

                               SPAGAIN;

       XPUSHi  Push an integer onto the stack, extending the stack if necessary.  Handles 'set' magic.  Uses "TARG",
               so "dTARGET" or "dXSTARG" should be called to declare it.  Do not call multiple "TARG"-oriented macros
               to return lists from XSUB's - see "mXPUSHi" instead.  See also "PUSHi" and "mPUSHi".

                       void    XPUSHi(IV iv)

       XPUSHmortal
               Push a new mortal SV onto the stack, extending the stack if necessary.  Does not use "TARG".  See also
               "XPUSHs", "PUSHmortal" and "PUSHs".

                       void    XPUSHmortal()

       XPUSHn  Push a double onto the stack, extending the stack if necessary.  Handles 'set' magic.  Uses "TARG", so
               "dTARGET" or "dXSTARG" should be called to declare it.  Do not call multiple "TARG"-oriented macros to
               return lists from XSUB's - see "mXPUSHn" instead.  See also "PUSHn" and "mPUSHn".

                       void    XPUSHn(NV nv)


       XPUSHu  Push an unsigned integer onto the stack, extending the stack if necessary.  Handles 'set' magic.  Uses
               "TARG", so "dTARGET" or "dXSTARG" should be called to declare it.  Do not call multiple
               "TARG"-oriented macros to return lists from XSUB's - see "mXPUSHu" instead.  See also "PUSHu" and
               "mPUSHu".

                       void    XPUSHu(UV uv)

       XSRETURN
               Return from XSUB, indicating number of items on the stack.  This is usually handled by "xsubpp".

                       void    XSRETURN(int nitems)

       XSRETURN_EMPTY
               Return an empty list from an XSUB immediately.

                               XSRETURN_EMPTY;

       XSRETURN_IV
               Return an integer from an XSUB immediately.  Uses "XST_mIV".

                       void    XSRETURN_IV(IV iv)

       XSRETURN_NO
               Return &PL_sv_no from an XSUB immediately.  Uses "XST_mNO".

                               XSRETURN_NO;

       XSRETURN_NV
               Return a double from an XSUB immediately.  Uses "XST_mNV".

                       void    XSRETURN_NV(NV nv)

       XSRETURN_PV
               Return a copy of a string from an XSUB immediately.  Uses "XST_mPV".

                       void    XSRETURN_PV(char* str)

       XSRETURN_UNDEF
               Return &PL_sv_undef from an XSUB immediately.  Uses "XST_mUNDEF".

                               XSRETURN_UNDEF;

       XSRETURN_UV
               Return an integer from an XSUB immediately.  Uses "XST_mUV".

                       void    XSRETURN_UV(IV uv)

       XSRETURN_YES
               Return &PL_sv_yes from an XSUB immediately.  Uses "XST_mYES".

                               XSRETURN_YES;

       XST_mIV Place an integer into the specified position "pos" on the stack.  The value is stored in a new mortal
               SV.

       XST_mPV Place a copy of a string into the specified position "pos" on the stack.  The value is stored in a new
               mortal SV.

                       void    XST_mPV(int pos, char* str)

       XST_mUNDEF
               Place &PL_sv_undef into the specified position "pos" on the stack.

                       void    XST_mUNDEF(int pos)

       XST_mYES
               Place &PL_sv_yes into the specified position "pos" on the stack.

                       void    XST_mYES(int pos)

SV Flags
       svtype  An enum of flags for Perl types.  These are found in the file sv.h in the "svtype" enum.  Test these
               flags with the "SvTYPE" macro.

       SVt_IV  Integer type flag for scalars.  See "svtype".

       SVt_NV  Double type flag for scalars.  See "svtype".

       SVt_PV  Pointer type flag for scalars.  See "svtype".

       SVt_PVAV
               Type flag for arrays.  See "svtype".

       SVt_PVCV
               Type flag for code refs.  See "svtype".

       SVt_PVHV
               Type flag for hashes.  See "svtype".

       SVt_PVMG
               Type flag for blessed scalars.  See "svtype".

SV Manipulation Functions
       boolSV  Returns a true SV if "b" is a true value, or a false SV if "b" is 0.

               See also "PL_sv_yes" and "PL_sv_no".

                       SV *    boolSV(bool b)

       croak_xs_usage
               A specialised variant of "croak()" for emitting the usage message for xsubs

                   croak_xs_usage(cv, "eee_yow");

               works out the package name and subroutine name from "cv", and then calls "croak()". Hence if "cv" is
               &ouch::awk, it would call "croak" as:

                   Perl_croak(aTHX_ "Usage: %"SVf"::%"SVf"(%s)", "ouch" "awk", "eee_yow");


               Creates an RV wrapper for an SV.  The reference count for the original SV is incremented.

                       SV*     newRV_inc(SV* sv)

       newSVpvn_utf8
               Creates a new SV and copies a string into it.  If utf8 is true, calls "SvUTF8_on" on the new SV.
               Implemented as a wrapper around "newSVpvn_flags".

                       SV*     newSVpvn_utf8(NULLOK const char* s, STRLEN len,
                                             U32 utf8)

       SvCUR   Returns the length of the string which is in the SV.  See "SvLEN".

                       STRLEN  SvCUR(SV* sv)

       SvCUR_set
               Set the current length of the string which is in the SV.  See "SvCUR" and "SvIV_set".

                       void    SvCUR_set(SV* sv, STRLEN len)

       SvEND   Returns a pointer to the spot just after the last character in the string which is in the SV, where
               there is usually a trailing null (even though Perl scalars do not strictly require it).  See "SvCUR".
               Access the character as *(SvEND(sv)).

               Warning: If "SvCUR" is equal to "SvLEN", then "SvEND" points to unallocated memory.

                       char*   SvEND(SV* sv)

       SvGAMAGIC
               Returns true if the SV has get magic or overloading.  If either is true then the scalar is active
               data, and has the potential to return a new value every time it is accessed.  Hence you must be
               careful to only read it once per user logical operation and work with that returned value.  If neither
               is true then the scalar's value cannot change unless written to.

                       U32     SvGAMAGIC(SV* sv)

       SvGROW  Expands the character buffer in the SV so that it has room for the indicated number of bytes (remember
               to reserve space for an extra trailing NUL character).  Calls "sv_grow" to perform the expansion if
               necessary.  Returns a pointer to the character buffer.

                       char *  SvGROW(SV* sv, STRLEN len)

       SvIOK   Returns a U32 value indicating whether the SV contains an integer.

                       U32     SvIOK(SV* sv)

       SvIOKp  Returns a U32 value indicating whether the SV contains an integer.  Checks the private setting.  Use
               "SvIOK" instead.

                       U32     SvIOKp(SV* sv)

       SvIOK_notUV
               Returns a boolean indicating whether the SV contains a signed integer.


       SvIOK_only
               Tells an SV that it is an integer and disables all other OK bits.

                       void    SvIOK_only(SV* sv)

       SvIOK_only_UV
               Tells and SV that it is an unsigned integer and disables all other OK bits.

                       void    SvIOK_only_UV(SV* sv)

       SvIOK_UV
               Returns a boolean indicating whether the SV contains an unsigned integer.

                       bool    SvIOK_UV(SV* sv)

       SvIsCOW Returns a boolean indicating whether the SV is Copy-On-Write (either shared hash key scalars, or full
               Copy On Write scalars if 5.9.0 is configured for COW).

                       bool    SvIsCOW(SV* sv)

       SvIsCOW_shared_hash
               Returns a boolean indicating whether the SV is Copy-On-Write shared hash key scalar.

                       bool    SvIsCOW_shared_hash(SV* sv)

       SvIV    Coerces the given SV to an integer and returns it.  See "SvIVx" for a version which guarantees to
               evaluate sv only once.

                       IV      SvIV(SV* sv)

       SvIVX   Returns the raw value in the SV's IV slot, without checks or conversions.  Only use when you are sure
               SvIOK is true.  See also "SvIV()".

                       IV      SvIVX(SV* sv)

       SvIVx   Coerces the given SV to an integer and returns it.  Guarantees to evaluate "sv" only once.  Only use
               this if "sv" is an expression with side effects, otherwise use the more efficient "SvIV".

                       IV      SvIVx(SV* sv)

       SvIV_nomg
               Like "SvIV" but doesn't process magic.

                       IV      SvIV_nomg(SV* sv)

       SvIV_set
               Set the value of the IV pointer in sv to val.  It is possible to perform the same function of this
               macro with an lvalue assignment to "SvIVX".  With future Perls, however, it will be more efficient to
               use "SvIV_set" instead of the lvalue assignment to "SvIVX".

                       void    SvIV_set(SV* sv, IV val)

       SvLEN   Returns the size of the string buffer in the SV, not including any part attributable to "SvOOK".  See
               "SvCUR".

       SvNIOK  Returns a U32 value indicating whether the SV contains a number, integer or double.

                       U32     SvNIOK(SV* sv)

       SvNIOKp Returns a U32 value indicating whether the SV contains a number, integer or double.  Checks the
               private setting.  Use "SvNIOK" instead.

                       U32     SvNIOKp(SV* sv)

       SvNIOK_off
               Unsets the NV/IV status of an SV.

                       void    SvNIOK_off(SV* sv)

       SvNOK   Returns a U32 value indicating whether the SV contains a double.

                       U32     SvNOK(SV* sv)

       SvNOKp  Returns a U32 value indicating whether the SV contains a double.  Checks the private setting.  Use
               "SvNOK" instead.

                       U32     SvNOKp(SV* sv)

       SvNOK_off
               Unsets the NV status of an SV.

                       void    SvNOK_off(SV* sv)

       SvNOK_on
               Tells an SV that it is a double.

                       void    SvNOK_on(SV* sv)

       SvNOK_only
               Tells an SV that it is a double and disables all other OK bits.

                       void    SvNOK_only(SV* sv)

       SvNV    Coerce the given SV to a double and return it.  See "SvNVx" for a version which guarantees to evaluate
               sv only once.

                       NV      SvNV(SV* sv)

       SvNVX   Returns the raw value in the SV's NV slot, without checks or conversions.  Only use when you are sure
               SvNOK is true.  See also "SvNV()".

                       NV      SvNVX(SV* sv)

       SvNVx   Coerces the given SV to a double and returns it.  Guarantees to evaluate "sv" only once.  Only use
               this if "sv" is an expression with side effects, otherwise use the more efficient "SvNV".

                       NV      SvNVx(SV* sv)

                       U32     SvOK(SV* sv)

       SvOOK   Returns a U32 indicating whether the pointer to the string buffer is offset.  This hack is used
               internally to speed up removal of characters from the beginning of a SvPV.  When SvOOK is true, then
               the start of the allocated string buffer is actually "SvOOK_offset()" bytes before SvPVX.  This offset
               used to be stored in SvIVX, but is now stored within the spare part of the buffer.

                       U32     SvOOK(SV* sv)

       SvOOK_offset
               Reads into len the offset from SvPVX back to the true start of the allocated buffer, which will be
               non-zero if "sv_chop" has been used to efficiently remove characters from start of the buffer.
               Implemented as a macro, which takes the address of len, which must be of type "STRLEN".  Evaluates sv
               more than once.  Sets len to 0 if "SvOOK(sv)" is false.

                       void    SvOOK_offset(NN SV*sv, STRLEN len)

       SvPOK   Returns a U32 value indicating whether the SV contains a character string.

                       U32     SvPOK(SV* sv)

       SvPOKp  Returns a U32 value indicating whether the SV contains a character string.  Checks the private
               setting.  Use "SvPOK" instead.

                       U32     SvPOKp(SV* sv)

       SvPOK_off
               Unsets the PV status of an SV.

                       void    SvPOK_off(SV* sv)

       SvPOK_on
               Tells an SV that it is a string.

                       void    SvPOK_on(SV* sv)

       SvPOK_only
               Tells an SV that it is a string and disables all other OK bits.  Will also turn off the UTF-8 status.

                       void    SvPOK_only(SV* sv)

       SvPOK_only_UTF8
               Tells an SV that it is a string and disables all other OK bits, and leaves the UTF-8 status as it was.

                       void    SvPOK_only_UTF8(SV* sv)

       SvPV    Returns a pointer to the string in the SV, or a stringified form of the SV if the SV does not contain
               a string.  The SV may cache the stringified version becoming "SvPOK".  Handles 'get' magic.  See also
               "SvPVx" for a version which guarantees to evaluate sv only once.

                       char*   SvPV(SV* sv, STRLEN len)

       SvPVbyte
               Like "SvPV", but converts sv to byte representation first if necessary.

                       char*   SvPVbytex_force(SV* sv, STRLEN len)

       SvPVbyte_force
               Like "SvPV_force", but converts sv to byte representation first if necessary.

                       char*   SvPVbyte_force(SV* sv, STRLEN len)

       SvPVbyte_nolen
               Like "SvPV_nolen", but converts sv to byte representation first if necessary.

                       char*   SvPVbyte_nolen(SV* sv)

       SvPVutf8
               Like "SvPV", but converts sv to utf8 first if necessary.

                       char*   SvPVutf8(SV* sv, STRLEN len)

       SvPVutf8x
               Like "SvPV", but converts sv to utf8 first if necessary.  Guarantees to evaluate sv only once; use the
               more efficient "SvPVutf8" otherwise.

                       char*   SvPVutf8x(SV* sv, STRLEN len)

       SvPVutf8x_force
               Like "SvPV_force", but converts sv to utf8 first if necessary.  Guarantees to evaluate sv only once;
               use the more efficient "SvPVutf8_force" otherwise.

                       char*   SvPVutf8x_force(SV* sv, STRLEN len)

       SvPVutf8_force
               Like "SvPV_force", but converts sv to utf8 first if necessary.

                       char*   SvPVutf8_force(SV* sv, STRLEN len)

       SvPVutf8_nolen
               Like "SvPV_nolen", but converts sv to utf8 first if necessary.

                       char*   SvPVutf8_nolen(SV* sv)

       SvPVX   Returns a pointer to the physical string in the SV.  The SV must contain a string.

               This is also used to store the name of an autoloaded subroutine in an XS AUTOLOAD routine.  See
               "Autoloading with XSUBs" in perlguts.

                       char*   SvPVX(SV* sv)

       SvPVx   A version of "SvPV" which guarantees to evaluate "sv" only once.  Only use this if "sv" is an
               expression with side effects, otherwise use the more efficient "SvPV".

                       char*   SvPVx(SV* sv, STRLEN len)

       SvPV_force
               Like "SvPV" but will force the SV into containing just a string ("SvPOK_only").  You want force if you
               a string.  The SV may cache the stringified form becoming "SvPOK".  Handles 'get' magic.

                       char*   SvPV_nolen(SV* sv)

       SvPV_nomg
               Like "SvPV" but doesn't process magic.

                       char*   SvPV_nomg(SV* sv, STRLEN len)

       SvPV_nomg_nolen
               Like "SvPV_nolen" but doesn't process magic.

                       char*   SvPV_nomg_nolen(SV* sv)

       SvPV_set
               Set the value of the PV pointer in sv to val.  See "SvIV_set".

                       void    SvPV_set(SV* sv, char* val)

       SvREFCNT
               Returns the value of the object's reference count.

                       U32     SvREFCNT(SV* sv)

       SvREFCNT_dec
               Decrements the reference count of the given SV.

                       void    SvREFCNT_dec(SV* sv)

       SvREFCNT_inc
               Increments the reference count of the given SV.

               All of the following SvREFCNT_inc* macros are optimized versions of SvREFCNT_inc, and can be replaced
               with SvREFCNT_inc.

                       SV*     SvREFCNT_inc(SV* sv)

       SvREFCNT_inc_NN
               Same as SvREFCNT_inc, but can only be used if you know sv is not NULL.  Since we don't have to check
               the NULLness, it's faster and smaller.

                       SV*     SvREFCNT_inc_NN(SV* sv)

       SvREFCNT_inc_simple
               Same as SvREFCNT_inc, but can only be used with expressions without side effects.  Since we don't have
               to store a temporary value, it's faster.

                       SV*     SvREFCNT_inc_simple(SV* sv)

       SvREFCNT_inc_simple_NN
               Same as SvREFCNT_inc_simple, but can only be used if you know sv is not NULL.  Since we don't have to
               check the NULLness, it's faster and smaller.

                       SV*     SvREFCNT_inc_simple_NN(SV* sv)
                       void    SvREFCNT_inc_simple_void_NN(SV* sv)

       SvREFCNT_inc_void
               Same as SvREFCNT_inc, but can only be used if you don't need the return value.  The macro doesn't need
               to return a meaningful value.

                       void    SvREFCNT_inc_void(SV* sv)

       SvREFCNT_inc_void_NN
               Same as SvREFCNT_inc, but can only be used if you don't need the return value, and you know that sv is
               not NULL.  The macro doesn't need to return a meaningful value, or check for NULLness, so it's smaller
               and faster.

                       void    SvREFCNT_inc_void_NN(SV* sv)

       SvROK   Tests if the SV is an RV.

                       U32     SvROK(SV* sv)

       SvROK_off
               Unsets the RV status of an SV.

                       void    SvROK_off(SV* sv)

       SvROK_on
               Tells an SV that it is an RV.

                       void    SvROK_on(SV* sv)

       SvRV    Dereferences an RV to return the SV.

                       SV*     SvRV(SV* sv)

       SvRV_set
               Set the value of the RV pointer in sv to val.  See "SvIV_set".

                       void    SvRV_set(SV* sv, SV* val)

       SvSTASH Returns the stash of the SV.

                       HV*     SvSTASH(SV* sv)

       SvSTASH_set
               Set the value of the STASH pointer in sv to val.  See "SvIV_set".

                       void    SvSTASH_set(SV* sv, HV* val)

       SvTAINT Taints an SV if tainting is enabled, and if some input to the current expression is tainted--usually a
               variable, but possibly also implicit inputs such as locale settings.  "SvTAINT" propagates that
               taintedness to the outputs of an expression in a pessimistic fashion; i.e., without paying attention
               to precisely which outputs are influenced by which inputs.

                       void    SvTAINT(SV* sv)


       SvTAINTED_on
               Marks an SV as tainted if tainting is enabled.

                       void    SvTAINTED_on(SV* sv)

       SvTRUE  Returns a boolean indicating whether Perl would evaluate the SV as true or false.  See SvOK() for a
               defined/undefined test.  Handles 'get' magic unless the scalar is already SvPOK, SvIOK or SvNOK (the
               public, not the private flags).

                       bool    SvTRUE(SV* sv)

       SvTRUE_nomg
               Returns a boolean indicating whether Perl would evaluate the SV as true or false.  See SvOK() for a
               defined/undefined test.  Does not handle 'get' magic.

                       bool    SvTRUE_nomg(SV* sv)

       SvTYPE  Returns the type of the SV.  See "svtype".

                       svtype  SvTYPE(SV* sv)

       SvUOK   Returns a boolean indicating whether the SV contains an unsigned integer.

                       bool    SvUOK(SV* sv)

       SvUPGRADE
               Used to upgrade an SV to a more complex form.  Uses "sv_upgrade" to perform the upgrade if necessary.
               See "svtype".

                       void    SvUPGRADE(SV* sv, svtype type)

       SvUTF8  Returns a U32 value indicating the UTF-8 status of an SV.  If things are set-up properly, this
               indicates whether or not the SV contains UTF-8 encoded data.  Call this after SvPV() in case any call
               to string overloading updates the internal flag.

                       U32     SvUTF8(SV* sv)

       SvUTF8_off
               Unsets the UTF-8 status of an SV (the data is not changed, just the flag).  Do not use frivolously.

                       void    SvUTF8_off(SV *sv)

       SvUTF8_on
               Turn on the UTF-8 status of an SV (the data is not changed, just the flag).  Do not use frivolously.

                       void    SvUTF8_on(SV *sv)

       SvUV    Coerces the given SV to an unsigned integer and returns it.  See "SvUVx" for a version which
               guarantees to evaluate sv only once.

                       UV      SvUV(SV* sv)

       SvUVX   Returns the raw value in the SV's UV slot, without checks or conversions.  Only use when you are sure

                       UV      SvUV_nomg(SV* sv)

       SvUV_set
               Set the value of the UV pointer in sv to val.  See "SvIV_set".

                       void    SvUV_set(SV* sv, UV val)

       SvVOK   Returns a boolean indicating whether the SV contains a v-string.

                       bool    SvVOK(SV* sv)

       sv_catpvn_nomg
               Like "sv_catpvn" but doesn't process magic.

                       void    sv_catpvn_nomg(SV* sv, const char* ptr,
                                              STRLEN len)

       sv_catpv_nomg
               Like "sv_catpv" but doesn't process magic.

                       void    sv_catpv_nomg(SV* sv, const char* ptr)

       sv_catsv_nomg
               Like "sv_catsv" but doesn't process magic.

                       void    sv_catsv_nomg(SV* dsv, SV* ssv)

       sv_derived_from
               Exactly like "sv_derived_from_pv", but doesn't take a "flags" parameter.

                       bool    sv_derived_from(SV* sv, const char *const name)

       sv_derived_from_pv
               Exactly like "sv_derived_from_pvn", but takes a nul-terminated string instead of a string/length pair.

                       bool    sv_derived_from_pv(SV* sv,
                                                  const char *const name,
                                                  U32 flags)

       sv_derived_from_pvn
               Returns a boolean indicating whether the SV is derived from the specified class at the C level.  To
               check derivation at the Perl level, call "isa()" as a normal Perl method.

               Currently, the only significant value for "flags" is SVf_UTF8.

                       bool    sv_derived_from_pvn(SV* sv,
                                                   const char *const name,
                                                   const STRLEN len, U32 flags)

       sv_derived_from_sv
               Exactly like "sv_derived_from_pvn", but takes the name string in the form of an SV instead of a
               string/length pair.

                       bool    sv_derived_from_sv(SV* sv, SV *namesv,

       sv_does_pvn
               Like "sv_does_sv", but takes a string/length pair instead of an SV.

                       bool    sv_does_pvn(SV* sv, const char *const name,
                                           const STRLEN len, U32 flags)

       sv_does_sv
               Returns a boolean indicating whether the SV performs a specific, named role.  The SV can be a Perl
               object or the name of a Perl class.

                       bool    sv_does_sv(SV* sv, SV* namesv, U32 flags)

       sv_report_used
               Dump the contents of all SVs not yet freed (debugging aid).

                       void    sv_report_used()

       sv_setsv_nomg
               Like "sv_setsv" but doesn't process magic.

                       void    sv_setsv_nomg(SV* dsv, SV* ssv)

       sv_utf8_upgrade_nomg
               Like sv_utf8_upgrade, but doesn't do magic on "sv".

                       STRLEN  sv_utf8_upgrade_nomg(NN SV *sv)

SV-Body Allocation
       looks_like_number
               Test if the content of an SV looks like a number (or is a number).  "Inf" and "Infinity" are treated
               as numbers (so will not issue a non-numeric warning), even if your atof() doesn't grok them.  Get-
               magic is ignored.

                       I32     looks_like_number(SV *const sv)

       newRV_noinc
               Creates an RV wrapper for an SV.  The reference count for the original SV is not incremented.

                       SV*     newRV_noinc(SV *const sv)

       newSV   Creates a new SV.  A non-zero "len" parameter indicates the number of bytes of preallocated string
               space the SV should have.  An extra byte for a trailing NUL is also reserved.  (SvPOK is not set for
               the SV even if string space is allocated.)  The reference count for the new SV is set to 1.

               In 5.9.3, newSV() replaces the older NEWSV() API, and drops the first parameter, x, a debug aid which
               allowed callers to identify themselves.  This aid has been superseded by a new build option,
               PERL_MEM_LOG (see "PERL_MEM_LOG" in perlhacktips).  The older API is still there for use in XS modules
               supporting older perls.

                       SV*     newSV(const STRLEN len)

       newSVhek
               Creates a new SV from the hash key structure.  It will generate scalars that point to the shared
               string table where possible.  Returns a new (undefined) SV if the hek is NULL.

       newSVpv Creates a new SV and copies a string into it.  The reference count for the SV is set to 1.  If "len"
               is zero, Perl will compute the length using strlen().  For efficiency, consider using "newSVpvn"
               instead.

                       SV*     newSVpv(const char *const s, const STRLEN len)

       newSVpvf
               Creates a new SV and initializes it with the string formatted like "sprintf".

                       SV*     newSVpvf(const char *const pat, ...)

       newSVpvn
               Creates a new SV and copies a buffer into it, which may contain NUL characters ("\0") and other binary
               data.  The reference count for the SV is set to 1.  Note that if "len" is zero, Perl will create a
               zero length (Perl) string.  You are responsible for ensuring that the source buffer is at least "len"
               bytes long.  If the "buffer" argument is NULL the new SV will be undefined.

                       SV*     newSVpvn(const char *const s, const STRLEN len)

       newSVpvn_flags
               Creates a new SV and copies a string into it.  The reference count for the SV is set to 1.  Note that
               if "len" is zero, Perl will create a zero length string.  You are responsible for ensuring that the
               source string is at least "len" bytes long.  If the "s" argument is NULL the new SV will be undefined.
               Currently the only flag bits accepted are "SVf_UTF8" and "SVs_TEMP".  If "SVs_TEMP" is set, then
               "sv_2mortal()" is called on the result before returning.  If "SVf_UTF8" is set, "s" is considered to
               be in UTF-8 and the "SVf_UTF8" flag will be set on the new SV.  "newSVpvn_utf8()" is a convenience
               wrapper for this function, defined as

                   #define newSVpvn_utf8(s, len, u)                    \
                       newSVpvn_flags((s), (len), (u) ? SVf_UTF8 : 0)

                       SV*     newSVpvn_flags(const char *const s,
                                              const STRLEN len,
                                              const U32 flags)

       newSVpvn_share
               Creates a new SV with its SvPVX_const pointing to a shared string in the string table.  If the string
               does not already exist in the table, it is created first.  Turns on READONLY and FAKE.  If the "hash"
               parameter is non-zero, that value is used; otherwise the hash is computed.  The string's hash can
               later be retrieved from the SV with the "SvSHARED_HASH()" macro.  The idea here is that as the string
               table is used for shared hash keys these strings will have SvPVX_const == HeKEY and hash lookup will
               avoid string compare.

                       SV*     newSVpvn_share(const char* s, I32 len, U32 hash)

       newSVpvs
               Like "newSVpvn", but takes a literal string instead of a string/length pair.

                       SV*     newSVpvs(const char* s)

       newSVpvs_flags
               Like "newSVpvn_flags", but takes a literal string instead of a string/length pair.

                       SV*     newSVpvs_flags(const char* s, U32 flags)

       newSVrv Creates a new SV for the RV, "rv", to point to.  If "rv" is not an RV then it will be upgraded to one.
               If "classname" is non-null then the new SV will be blessed in the specified package.  The new SV is
               returned and its reference count is 1.

                       SV*     newSVrv(SV *const rv,
                                       const char *const classname)

       newSVsv Creates a new SV which is an exact duplicate of the original SV.  (Uses "sv_setsv".)

                       SV*     newSVsv(SV *const old)

       newSVuv Creates a new SV and copies an unsigned integer into it.  The reference count for the SV is set to 1.

                       SV*     newSVuv(const UV u)

       newSV_type
               Creates a new SV, of the type specified.  The reference count for the new SV is set to 1.

                       SV*     newSV_type(const svtype type)

       sv_2bool
               This macro is only used by sv_true() or its macro equivalent, and only if the latter's argument is
               neither SvPOK, SvIOK nor SvNOK.  It calls sv_2bool_flags with the SV_GMAGIC flag.

                       bool    sv_2bool(SV *const sv)

       sv_2bool_flags
               This function is only used by sv_true() and friends,  and only if the latter's argument is neither
               SvPOK, SvIOK nor SvNOK.  If the flags contain SV_GMAGIC, then it does an mg_get() first.

                       bool    sv_2bool_flags(SV *const sv, const I32 flags)

       sv_2cv  Using various gambits, try to get a CV from an SV; in addition, try if possible to set *st and *gvp to
               the stash and GV associated with it.  The flags in "lref" are passed to gv_fetchsv.

                       CV*     sv_2cv(SV* sv, HV **const st, GV **const gvp,
                                      const I32 lref)

       sv_2io  Using various gambits, try to get an IO from an SV: the IO slot if its a GV; or the recursive result
               if we're an RV; or the IO slot of the symbol named after the PV if we're a string.

               'Get' magic is ignored on the sv passed in, but will be called on "SvRV(sv)" if sv is an RV.

                       IO*     sv_2io(SV *const sv)

       sv_2iv_flags
               Return the integer value of an SV, doing any necessary string conversion.  If flags includes
               SV_GMAGIC, does an mg_get() first.  Normally used via the "SvIV(sv)" and "SvIVx(sv)" macros.

                       IV      sv_2iv_flags(SV *const sv, const I32 flags)

       sv_2mortal
               Marks an existing SV as mortal.  The SV will be destroyed "soon", either by an explicit call to
               FREETMPS, or by an implicit call at places such as statement boundaries.  SvTEMP() is turned on which
               Return a pointer to the byte-encoded representation of the SV, and set *lp to its length.  May cause
               the SV to be downgraded from UTF-8 as a side-effect.

               Usually accessed via the "SvPVbyte" macro.

                       char*   sv_2pvbyte(SV *sv, STRLEN *const lp)

       sv_2pvutf8
               Return a pointer to the UTF-8-encoded representation of the SV, and set *lp to its length.  May cause
               the SV to be upgraded to UTF-8 as a side-effect.

               Usually accessed via the "SvPVutf8" macro.

                       char*   sv_2pvutf8(SV *sv, STRLEN *const lp)

       sv_2pv_flags
               Returns a pointer to the string value of an SV, and sets *lp to its length.  If flags includes
               SV_GMAGIC, does an mg_get() first.  Coerces sv to a string if necessary.  Normally invoked via the
               "SvPV_flags" macro.  "sv_2pv()" and "sv_2pv_nomg" usually end up here too.

                       char*   sv_2pv_flags(SV *const sv, STRLEN *const lp,
                                            const I32 flags)

       sv_2uv_flags
               Return the unsigned integer value of an SV, doing any necessary string conversion.  If flags includes
               SV_GMAGIC, does an mg_get() first.  Normally used via the "SvUV(sv)" and "SvUVx(sv)" macros.

                       UV      sv_2uv_flags(SV *const sv, const I32 flags)

       sv_backoff
               Remove any string offset.  You should normally use the "SvOOK_off" macro wrapper instead.

                       int     sv_backoff(SV *const sv)

       sv_bless
               Blesses an SV into a specified package.  The SV must be an RV.  The package must be designated by its
               stash (see "gv_stashpv()").  The reference count of the SV is unaffected.

                       SV*     sv_bless(SV *const sv, HV *const stash)

       sv_catpv
               Concatenates the string onto the end of the string which is in the SV.  If the SV has the UTF-8 status
               set, then the bytes appended should be valid UTF-8.  Handles 'get' magic, but not 'set' magic.  See
               "sv_catpv_mg".

                       void    sv_catpv(SV *const sv, const char* ptr)

       sv_catpvf
               Processes its arguments like "sprintf" and appends the formatted output to an SV.  If the appended
               data contains "wide" characters (including, but not limited to, SVs with a UTF-8 PV formatted with %s,
               and characters >255 formatted with %c), the original SV might get upgraded to UTF-8.  Handles 'get'
               magic, but not 'set' magic.  See "sv_catpvf_mg".  If the original SV was UTF-8, the pattern should be
               valid UTF-8; if the original SV was bytes, the pattern should be too.

               Handles 'get' magic, but not 'set' magic.  See "sv_catpvn_mg".

                       void    sv_catpvn(SV *dsv, const char *sstr, STRLEN len)

       sv_catpvn_flags
               Concatenates the string onto the end of the string which is in the SV.  The "len" indicates number of
               bytes to copy.  If the SV has the UTF-8 status set, then the bytes appended should be valid UTF-8.  If
               "flags" has the "SV_SMAGIC" bit set, will "mg_set" on "dsv" afterwards if appropriate.  "sv_catpvn"
               and "sv_catpvn_nomg" are implemented in terms of this function.

                       void    sv_catpvn_flags(SV *const dstr,
                                               const char *sstr,
                                               const STRLEN len,
                                               const I32 flags)

       sv_catpvs
               Like "sv_catpvn", but takes a literal string instead of a string/length pair.

                       void    sv_catpvs(SV* sv, const char* s)

       sv_catpvs_flags
               Like "sv_catpvn_flags", but takes a literal string instead of a string/length pair.

                       void    sv_catpvs_flags(SV* sv, const char* s,
                                               I32 flags)

       sv_catpvs_mg
               Like "sv_catpvn_mg", but takes a literal string instead of a string/length pair.

                       void    sv_catpvs_mg(SV* sv, const char* s)

       sv_catpvs_nomg
               Like "sv_catpvn_nomg", but takes a literal string instead of a string/length pair.

                       void    sv_catpvs_nomg(SV* sv, const char* s)

       sv_catpv_flags
               Concatenates the string onto the end of the string which is in the SV.  If the SV has the UTF-8 status
               set, then the bytes appended should be valid UTF-8.  If "flags" has the "SV_SMAGIC" bit set, will
               "mg_set" on the modified SV if appropriate.

                       void    sv_catpv_flags(SV *dstr, const char *sstr,
                                              const I32 flags)

       sv_catpv_mg
               Like "sv_catpv", but also handles 'set' magic.

                       void    sv_catpv_mg(SV *const sv, const char *const ptr)

       sv_catsv
               Concatenates the string from SV "ssv" onto the end of the string in SV "dsv".  Modifies "dsv" but not
               "ssv".  Handles 'get' magic, but not 'set' magic.  See "sv_catsv_mg".

                       void    sv_catsv(SV *dstr, SV *sstr)

               character of the adjusted string.  Uses the "OOK hack".

               Beware: after this function returns, "ptr" and SvPVX_const(sv) may no longer refer to the same chunk
               of data.

               The unfortunate similarity of this function's name to that of Perl's "chop" operator is strictly
               coincidental.  This function works from the left; "chop" works from the right.

                       void    sv_chop(SV *const sv, const char *const ptr)

       sv_clear
               Clear an SV: call any destructors, free up any memory used by the body, and free the body itself.  The
               SV's head is not freed, although its type is set to all 1's so that it won't inadvertently be assumed
               to be live during global destruction etc.  This function should only be called when REFCNT is zero.
               Most of the time you'll want to call "sv_free()" (or its macro wrapper "SvREFCNT_dec") instead.

                       void    sv_clear(SV *const orig_sv)

       sv_cmp  Compares the strings in two SVs.  Returns -1, 0, or 1 indicating whether the string in "sv1" is less
               than, equal to, or greater than the string in "sv2".  Is UTF-8 and 'use bytes' aware, handles get
               magic, and will coerce its args to strings if necessary.  See also "sv_cmp_locale".

                       I32     sv_cmp(SV *const sv1, SV *const sv2)

       sv_cmp_flags
               Compares the strings in two SVs.  Returns -1, 0, or 1 indicating whether the string in "sv1" is less
               than, equal to, or greater than the string in "sv2".  Is UTF-8 and 'use bytes' aware and will coerce
               its args to strings if necessary.  If the flags include SV_GMAGIC, it handles get magic.  See also
               "sv_cmp_locale_flags".

                       I32     sv_cmp_flags(SV *const sv1, SV *const sv2,
                                            const U32 flags)

       sv_cmp_locale
               Compares the strings in two SVs in a locale-aware manner.  Is UTF-8 and 'use bytes' aware, handles get
               magic, and will coerce its args to strings if necessary.  See also "sv_cmp".

                       I32     sv_cmp_locale(SV *const sv1, SV *const sv2)

       sv_cmp_locale_flags
               Compares the strings in two SVs in a locale-aware manner.  Is UTF-8 and 'use bytes' aware and will
               coerce its args to strings if necessary.  If the flags contain SV_GMAGIC, it handles get magic.  See
               also "sv_cmp_flags".

                       I32     sv_cmp_locale_flags(SV *const sv1,
                                                   SV *const sv2,
                                                   const U32 flags)

       sv_collxfrm
               This calls "sv_collxfrm_flags" with the SV_GMAGIC flag.  See "sv_collxfrm_flags".

                       char*   sv_collxfrm(SV *const sv, STRLEN *const nxp)

       sv_collxfrm_flags

               Copies a stringified representation of the source SV into the destination SV.  Automatically performs
               any necessary mg_get and coercion of numeric values into strings.  Guaranteed to preserve UTF8 flag
               even from overloaded objects.  Similar in nature to sv_2pv[_flags] but operates directly on an SV
               instead of just the string.  Mostly uses sv_2pv_flags to do its work, except when that would lose the
               UTF-8'ness of the PV.

                       void    sv_copypv(SV *const dsv, SV *const ssv)

       sv_dec  Auto-decrement of the value in the SV, doing string to numeric conversion if necessary.  Handles 'get'
               magic and operator overloading.

                       void    sv_dec(SV *const sv)

       sv_dec_nomg
               Auto-decrement of the value in the SV, doing string to numeric conversion if necessary.  Handles
               operator overloading.  Skips handling 'get' magic.

                       void    sv_dec_nomg(SV *const sv)

       sv_eq   Returns a boolean indicating whether the strings in the two SVs are identical.  Is UTF-8 and 'use
               bytes' aware, handles get magic, and will coerce its args to strings if necessary.

                       I32     sv_eq(SV* sv1, SV* sv2)

       sv_eq_flags
               Returns a boolean indicating whether the strings in the two SVs are identical.  Is UTF-8 and 'use
               bytes' aware and coerces its args to strings if necessary.  If the flags include SV_GMAGIC, it handles
               get-magic, too.

                       I32     sv_eq_flags(SV* sv1, SV* sv2, const U32 flags)

       sv_force_normal_flags
               Undo various types of fakery on an SV: if the PV is a shared string, make a private copy; if we're a
               ref, stop refing; if we're a glob, downgrade to an xpvmg; if we're a copy-on-write scalar, this is the
               on-write time when we do the copy, and is also used locally.  If "SV_COW_DROP_PV" is set then a copy-
               on-write scalar drops its PV buffer (if any) and becomes SvPOK_off rather than making a copy.  (Used
               where this scalar is about to be set to some other value.)  In addition, the "flags" parameter gets
               passed to "sv_unref_flags()" when unreffing.  "sv_force_normal" calls this function with flags set to
               0.

                       void    sv_force_normal_flags(SV *const sv,
                                                     const U32 flags)

       sv_free Decrement an SV's reference count, and if it drops to zero, call "sv_clear" to invoke destructors and
               free up any memory used by the body; finally, deallocate the SV's head itself.  Normally called via a
               wrapper macro "SvREFCNT_dec".

                       void    sv_free(SV *const sv)

       sv_gets Get a line from the filehandle and store it into the SV, optionally appending to the currently-stored
               string.

                       char*   sv_gets(SV *const sv, PerlIO *const fp,
                                       I32 append)

               Auto-increment of the value in the SV, doing string to numeric conversion if necessary.  Handles
               operator overloading.  Skips handling 'get' magic.

                       void    sv_inc_nomg(SV *const sv)

       sv_insert
               Inserts a string at the specified offset/length within the SV.  Similar to the Perl substr() function.
               Handles get magic.

                       void    sv_insert(SV *const bigstr, const STRLEN offset,
                                         const STRLEN len,
                                         const char *const little,
                                         const STRLEN littlelen)

       sv_insert_flags
               Same as "sv_insert", but the extra "flags" are passed to the "SvPV_force_flags" that applies to
               "bigstr".

                       void    sv_insert_flags(SV *const bigstr,
                                               const STRLEN offset,
                                               const STRLEN len,
                                               const char *const little,
                                               const STRLEN littlelen,
                                               const U32 flags)

       sv_isa  Returns a boolean indicating whether the SV is blessed into the specified class.  This does not check
               for subtypes; use "sv_derived_from" to verify an inheritance relationship.

                       int     sv_isa(SV* sv, const char *const name)

       sv_isobject
               Returns a boolean indicating whether the SV is an RV pointing to a blessed object.  If the SV is not
               an RV, or if the object is not blessed, then this will return false.

                       int     sv_isobject(SV* sv)

       sv_len  Returns the length of the string in the SV.  Handles magic and type coercion.  See also "SvCUR", which
               gives raw access to the xpv_cur slot.

                       STRLEN  sv_len(SV *const sv)

       sv_len_utf8
               Returns the number of characters in the string in an SV, counting wide UTF-8 bytes as a single
               character.  Handles magic and type coercion.

                       STRLEN  sv_len_utf8(SV *const sv)

       sv_magic
               Adds magic to an SV.  First upgrades "sv" to type "SVt_PVMG" if necessary, then adds a new magic item
               of type "how" to the head of the magic list.

               See "sv_magicext" (which "sv_magic" now calls) for a description of the handling of the "name" and
               "namlen" arguments.

               to SvREADONLY SVs, and add more than one instance of the same 'how'.

               If "namlen" is greater than zero then a "savepvn" copy of "name" is stored, if "namlen" is zero then
               "name" is stored as-is and - as another special case - if "(name && namlen == HEf_SVKEY)" then "name"
               is assumed to contain an "SV*" and is stored as-is with its REFCNT incremented.

               (This is now used as a subroutine by "sv_magic".)

                       MAGIC * sv_magicext(SV *const sv, SV *const obj,
                                           const int how,
                                           const MGVTBL *const vtbl,
                                           const char *const name,
                                           const I32 namlen)

       sv_mortalcopy
               Creates a new SV which is a copy of the original SV (using "sv_setsv").  The new SV is marked as
               mortal.  It will be destroyed "soon", either by an explicit call to FREETMPS, or by an implicit call
               at places such as statement boundaries.  See also "sv_newmortal" and "sv_2mortal".

                       SV*     sv_mortalcopy(SV *const oldsv)

       sv_newmortal
               Creates a new null SV which is mortal.  The reference count of the SV is set to 1.  It will be
               destroyed "soon", either by an explicit call to FREETMPS, or by an implicit call at places such as
               statement boundaries.  See also "sv_mortalcopy" and "sv_2mortal".

                       SV*     sv_newmortal()

       sv_newref
               Increment an SV's reference count.  Use the "SvREFCNT_inc()" wrapper instead.

                       SV*     sv_newref(SV *const sv)

       sv_pos_b2u
               Converts the value pointed to by offsetp from a count of bytes from the start of the string, to a
               count of the equivalent number of UTF-8 chars.  Handles magic and type coercion.

                       void    sv_pos_b2u(SV *const sv, I32 *const offsetp)

       sv_pos_u2b
               Converts the value pointed to by offsetp from a count of UTF-8 chars from the start of the string, to
               a count of the equivalent number of bytes; if lenp is non-zero, it does the same to lenp, but this
               time starting from the offset, rather than from the start of the string.  Handles magic and type
               coercion.

               Use "sv_pos_u2b_flags" in preference, which correctly handles strings longer than 2Gb.

                       void    sv_pos_u2b(SV *const sv, I32 *const offsetp,
                                          I32 *const lenp)

       sv_pos_u2b_flags
               Converts the value pointed to by offsetp from a count of UTF-8 chars from the start of the string, to
               a count of the equivalent number of bytes; if lenp is non-zero, it does the same to lenp, but this
               time starting from the offset, rather than from the start of the string.  Handles type coercion.
               compilers which can't cope with complex macro expressions.  Always use the macro instead.

                       char*   sv_pvn_force(SV* sv, STRLEN* lp)

       sv_pvn_force_flags
               Get a sensible string out of the SV somehow.  If "flags" has "SV_GMAGIC" bit set, will "mg_get" on
               "sv" if appropriate, else not.  "sv_pvn_force" and "sv_pvn_force_nomg" are implemented in terms of
               this function.  You normally want to use the various wrapper macros instead: see "SvPV_force" and
               "SvPV_force_nomg"

                       char*   sv_pvn_force_flags(SV *const sv,
                                                  STRLEN *const lp,
                                                  const I32 flags)

       sv_pvutf8n_force
               The backend for the "SvPVutf8x_force" macro.  Always use the macro instead.

                       char*   sv_pvutf8n_force(SV *const sv, STRLEN *const lp)

       sv_reftype
               Returns a string describing what the SV is a reference to.

                       const char* sv_reftype(const SV *const sv, const int ob)

       sv_replace
               Make the first argument a copy of the second, then delete the original.  The target SV physically
               takes over ownership of the body of the source SV and inherits its flags; however, the target keeps
               any magic it owns, and any magic in the source is discarded.  Note that this is a rather specialist SV
               copying operation; most of the time you'll want to use "sv_setsv" or one of its many macro front-ends.

                       void    sv_replace(SV *const sv, SV *const nsv)

       sv_reset
               Underlying implementation for the "reset" Perl function.  Note that the perl-level function is vaguely
               deprecated.

                       void    sv_reset(const char* s, HV *const stash)

       sv_rvweaken
               Weaken a reference: set the "SvWEAKREF" flag on this RV; give the referred-to SV "PERL_MAGIC_backref"
               magic if it hasn't already; and push a back-reference to this RV onto the array of backreferences
               associated with that magic.  If the RV is magical, set magic will be called after the RV is cleared.

                       SV*     sv_rvweaken(SV *const sv)

       sv_setiv
               Copies an integer into the given SV, upgrading first if necessary.  Does not handle 'set' magic.  See
               also "sv_setiv_mg".

                       void    sv_setiv(SV *const sv, const IV num)

       sv_setiv_mg
               Like "sv_setiv", but also handles 'set' magic.


       sv_setpv
               Copies a string into an SV.  The string must be null-terminated.  Does not handle 'set' magic.  See
               "sv_setpv_mg".

                       void    sv_setpv(SV *const sv, const char *const ptr)

       sv_setpvf
               Works like "sv_catpvf" but copies the text into the SV instead of appending it.  Does not handle 'set'
               magic.  See "sv_setpvf_mg".

                       void    sv_setpvf(SV *const sv, const char *const pat,
                                         ...)

       sv_setpvf_mg
               Like "sv_setpvf", but also handles 'set' magic.

                       void    sv_setpvf_mg(SV *const sv,
                                            const char *const pat, ...)

       sv_setpviv
               Copies an integer into the given SV, also updating its string value.  Does not handle 'set' magic.
               See "sv_setpviv_mg".

                       void    sv_setpviv(SV *const sv, const IV num)

       sv_setpviv_mg
               Like "sv_setpviv", but also handles 'set' magic.

                       void    sv_setpviv_mg(SV *const sv, const IV iv)

       sv_setpvn
               Copies a string into an SV.  The "len" parameter indicates the number of bytes to be copied.  If the
               "ptr" argument is NULL the SV will become undefined.  Does not handle 'set' magic.  See
               "sv_setpvn_mg".

                       void    sv_setpvn(SV *const sv, const char *const ptr,
                                         const STRLEN len)

       sv_setpvn_mg
               Like "sv_setpvn", but also handles 'set' magic.

                       void    sv_setpvn_mg(SV *const sv,
                                            const char *const ptr,
                                            const STRLEN len)

       sv_setpvs
               Like "sv_setpvn", but takes a literal string instead of a string/length pair.

                       void    sv_setpvs(SV* sv, const char* s)

       sv_setpvs_mg
               Like "sv_setpvn_mg", but takes a literal string instead of a string/length pair.


                       SV*     sv_setref_iv(SV *const rv,
                                            const char *const classname,
                                            const IV iv)

       sv_setref_nv
               Copies a double into a new SV, optionally blessing the SV.  The "rv" argument will be upgraded to an
               RV.  That RV will be modified to point to the new SV.  The "classname" argument indicates the package
               for the blessing.  Set "classname" to "NULL" to avoid the blessing.  The new SV will have a reference
               count of 1, and the RV will be returned.

                       SV*     sv_setref_nv(SV *const rv,
                                            const char *const classname,
                                            const NV nv)

       sv_setref_pv
               Copies a pointer into a new SV, optionally blessing the SV.  The "rv" argument will be upgraded to an
               RV.  That RV will be modified to point to the new SV.  If the "pv" argument is NULL then "PL_sv_undef"
               will be placed into the SV.  The "classname" argument indicates the package for the blessing.  Set
               "classname" to "NULL" to avoid the blessing.  The new SV will have a reference count of 1, and the RV
               will be returned.

               Do not use with other Perl types such as HV, AV, SV, CV, because those objects will become corrupted
               by the pointer copy process.

               Note that "sv_setref_pvn" copies the string while this copies the pointer.

                       SV*     sv_setref_pv(SV *const rv,
                                            const char *const classname,
                                            void *const pv)

       sv_setref_pvn
               Copies a string into a new SV, optionally blessing the SV.  The length of the string must be specified
               with "n".  The "rv" argument will be upgraded to an RV.  That RV will be modified to point to the new
               SV.  The "classname" argument indicates the package for the blessing.  Set "classname" to "NULL" to
               avoid the blessing.  The new SV will have a reference count of 1, and the RV will be returned.

               Note that "sv_setref_pv" copies the pointer while this copies the string.

                       SV*     sv_setref_pvn(SV *const rv,
                                             const char *const classname,
                                             const char *const pv,
                                             const STRLEN n)

       sv_setref_pvs
               Like "sv_setref_pvn", but takes a literal string instead of a string/length pair.

                       SV *    sv_setref_pvs(const char* s)

       sv_setref_uv
               Copies an unsigned integer into a new SV, optionally blessing the SV.  The "rv" argument will be
               upgraded to an RV.  That RV will be modified to point to the new SV.  The "classname" argument
               indicates the package for the blessing.  Set "classname" to "NULL" to avoid the blessing.  The new SV
               will have a reference count of 1, and the RV will be returned.
               "SvSetMagicSV" and "SvSetMagicSV_nosteal".

                       void    sv_setsv(SV *dstr, SV *sstr)

       sv_setsv_flags
               Copies the contents of the source SV "ssv" into the destination SV "dsv".  The source SV may be
               destroyed if it is mortal, so don't use this function if the source SV needs to be reused.  Does not
               handle 'set' magic.  Loosely speaking, it performs a copy-by-value, obliterating any previous content
               of the destination.  If the "flags" parameter has the "SV_GMAGIC" bit set, will "mg_get" on "ssv" if
               appropriate, else not.  If the "flags" parameter has the "NOSTEAL" bit set then the buffers of temps
               will not be stolen.  <sv_setsv> and "sv_setsv_nomg" are implemented in terms of this function.

               You probably want to use one of the assortment of wrappers, such as "SvSetSV", "SvSetSV_nosteal",
               "SvSetMagicSV" and "SvSetMagicSV_nosteal".

               This is the primary function for copying scalars, and most other copy-ish functions and macros use
               this underneath.

                       void    sv_setsv_flags(SV *dstr, SV *sstr,
                                              const I32 flags)

       sv_setsv_mg
               Like "sv_setsv", but also handles 'set' magic.

                       void    sv_setsv_mg(SV *const dstr, SV *const sstr)

       sv_setuv
               Copies an unsigned integer into the given SV, upgrading first if necessary.  Does not handle 'set'
               magic.  See also "sv_setuv_mg".

                       void    sv_setuv(SV *const sv, const UV num)

       sv_setuv_mg
               Like "sv_setuv", but also handles 'set' magic.

                       void    sv_setuv_mg(SV *const sv, const UV u)

       sv_tainted
               Test an SV for taintedness.  Use "SvTAINTED" instead.

                       bool    sv_tainted(SV *const sv)

       sv_true Returns true if the SV has a true value by Perl's rules.  Use the "SvTRUE" macro instead, which may
               call "sv_true()" or may instead use an in-line version.

                       I32     sv_true(SV *const sv)

       sv_unmagic
               Removes all magic of type "type" from an SV.

                       int     sv_unmagic(SV *const sv, const int type)

       sv_unmagicext
               Removes all magic of type "type" with the specified "vtbl" from an SV.

       sv_untaint
               Untaint an SV.  Use "SvTAINTED_off" instead.

                       void    sv_untaint(SV *const sv)

       sv_upgrade
               Upgrade an SV to a more complex form.  Generally adds a new body type to the SV, then copies across as
               much information as possible from the old body.  It croaks if the SV is already in a more complex form
               than requested.  You generally want to use the "SvUPGRADE" macro wrapper, which checks the type before
               calling "sv_upgrade", and hence does not croak.  See also "svtype".

                       void    sv_upgrade(SV *const sv, svtype new_type)

       sv_usepvn_flags
               Tells an SV to use "ptr" to find its string value.  Normally the string is stored inside the SV but
               sv_usepvn allows the SV to use an outside string.  The "ptr" should point to memory that was allocated
               by "malloc".  It must be the start of a mallocked block of memory, and not a pointer to the middle of
               it.  The string length, "len", must be supplied.  By default this function will realloc (i.e. move)
               the memory pointed to by "ptr", so that pointer should not be freed or used by the programmer after
               giving it to sv_usepvn, and neither should any pointers from "behind" that pointer (e.g. ptr + 1) be
               used.

               If "flags" & SV_SMAGIC is true, will call SvSETMAGIC.  If "flags" & SV_HAS_TRAILING_NUL is true, then
               "ptr[len]" must be NUL, and the realloc will be skipped (i.e. the buffer is actually at least 1 byte
               longer than "len", and already meets the requirements for storing in "SvPVX").

                       void    sv_usepvn_flags(SV *const sv, char* ptr,
                                               const STRLEN len,
                                               const U32 flags)

       sv_utf8_decode
               If the PV of the SV is an octet sequence in UTF-8 and contains a multiple-byte character, the "SvUTF8"
               flag is turned on so that it looks like a character.  If the PV contains only single-byte characters,
               the "SvUTF8" flag stays off.  Scans PV for validity and returns false if the PV is invalid UTF-8.

               NOTE: this function is experimental and may change or be removed without notice.

                       bool    sv_utf8_decode(SV *const sv)

       sv_utf8_downgrade
               Attempts to convert the PV of an SV from characters to bytes.  If the PV contains a character that
               cannot fit in a byte, this conversion will fail; in this case, either returns false or, if "fail_ok"
               is not true, croaks.

               This is not as a general purpose Unicode to byte encoding interface: use the Encode extension for
               that.

               NOTE: this function is experimental and may change or be removed without notice.

                       bool    sv_utf8_downgrade(SV *const sv,
                                                 const bool fail_ok)

       sv_utf8_encode

               that.

                       STRLEN  sv_utf8_upgrade(SV *sv)

       sv_utf8_upgrade_flags
               Converts the PV of an SV to its UTF-8-encoded form.  Forces the SV to string form if it is not
               already.  Always sets the SvUTF8 flag to avoid future validity checks even if all the bytes are
               invariant in UTF-8.  If "flags" has "SV_GMAGIC" bit set, will "mg_get" on "sv" if appropriate, else
               not.  Returns the number of bytes in the converted string "sv_utf8_upgrade" and "sv_utf8_upgrade_nomg"
               are implemented in terms of this function.

               This is not as a general purpose byte encoding to Unicode interface: use the Encode extension for
               that.

                       STRLEN  sv_utf8_upgrade_flags(SV *const sv,
                                                     const I32 flags)

       sv_utf8_upgrade_nomg
               Like sv_utf8_upgrade, but doesn't do magic on "sv".

                       STRLEN  sv_utf8_upgrade_nomg(SV *sv)

       sv_vcatpvf
               Processes its arguments like "vsprintf" and appends the formatted output to an SV.  Does not handle
               'set' magic.  See "sv_vcatpvf_mg".

               Usually used via its frontend "sv_catpvf".

                       void    sv_vcatpvf(SV *const sv, const char *const pat,
                                          va_list *const args)

       sv_vcatpvfn
               Processes its arguments like "vsprintf" and appends the formatted output to an SV.  Uses an array of
               SVs if the C style variable argument list is missing (NULL).  When running with taint checks enabled,
               indicates via "maybe_tainted" if results are untrustworthy (often due to the use of locales).

               Usually used via one of its frontends "sv_vcatpvf" and "sv_vcatpvf_mg".

                       void    sv_vcatpvfn(SV *const sv, const char *const pat,
                                           const STRLEN patlen,
                                           va_list *const args,
                                           SV **const svargs, const I32 svmax,
                                           bool *const maybe_tainted)

       sv_vcatpvf_mg
               Like "sv_vcatpvf", but also handles 'set' magic.

               Usually used via its frontend "sv_catpvf_mg".

                       void    sv_vcatpvf_mg(SV *const sv,
                                             const char *const pat,
                                             va_list *const args)

       sv_vsetpvf

                       void    sv_vsetpvfn(SV *const sv, const char *const pat,
                                           const STRLEN patlen,
                                           va_list *const args,
                                           SV **const svargs, const I32 svmax,
                                           bool *const maybe_tainted)

       sv_vsetpvf_mg
               Like "sv_vsetpvf", but also handles 'set' magic.

               Usually used via its frontend "sv_setpvf_mg".

                       void    sv_vsetpvf_mg(SV *const sv,
                                             const char *const pat,
                                             va_list *const args)

Unicode Support
       bytes_cmp_utf8
               Compares the sequence of characters (stored as octets) in "b", "blen" with the sequence of characters
               (stored as UTF-8) in "u", "ulen". Returns 0 if they are equal, -1 or -2 if the first string is less
               than the second string, +1 or +2 if the first string is greater than the second string.

               -1 or +1 is returned if the shorter string was identical to the start of the longer string. -2 or +2
               is returned if the was a difference between characters within the strings.

                       int     bytes_cmp_utf8(const U8 *b, STRLEN blen,
                                              const U8 *u, STRLEN ulen)

       bytes_from_utf8
               Converts a string "s" of length "len" from UTF-8 into native byte encoding.  Unlike "utf8_to_bytes"
               but like "bytes_to_utf8", returns a pointer to the newly-created string, and updates "len" to contain
               the new length.  Returns the original string if no conversion occurs, "len" is unchanged. Do nothing
               if "is_utf8" points to 0. Sets "is_utf8" to 0 if "s" is converted or consisted entirely of characters
               that are invariant in utf8 (i.e., US-ASCII on non-EBCDIC machines).

               NOTE: this function is experimental and may change or be removed without notice.

                       U8*     bytes_from_utf8(const U8 *s, STRLEN *len,
                                               bool *is_utf8)

       bytes_to_utf8
               Converts a string "s" of length "len" bytes from the native encoding into UTF-8.  Returns a pointer to
               the newly-created string, and sets "len" to reflect the new length in bytes.

               A NUL character will be written after the end of the string.

               If you want to convert to UTF-8 from encodings other than the native (Latin1 or EBCDIC), see
               "sv_recode_to_utf8"().

               NOTE: this function is experimental and may change or be removed without notice.

                       U8*     bytes_to_utf8(const U8 *s, STRLEN *len)

       foldEQ_utf8

               If "pe1" is non-NULL and the pointer it points to is not NULL, that pointer is considered an end
               pointer beyond which scanning of "s1" will not continue under any circumstances.  This means that if
               both "l1" and "pe1" are specified, and "pe1" is less than "s1"+"l1", the match will never be
               successful because it can never get as far as its goal (and in fact is asserted against).
               Correspondingly for "pe2" with respect to "s2".

               At least one of "s1" and "s2" must have a goal (at least one of "l1" and "l2" must be non-zero), and
               if both do, both have to be reached for a successful match.   Also, if the fold of a character is
               multiple characters, all of them must be matched (see tr21 reference below for 'folding').

               Upon a successful match, if "pe1" is non-NULL, it will be set to point to the beginning of the next
               character of "s1" beyond what was matched.  Correspondingly for "pe2" and "s2".

               For case-insensitiveness, the "casefolding" of Unicode is used instead of upper/lowercasing both the
               characters, see <http://www.unicode.org/unicode/reports/tr21/> (Case Mappings).

                       I32     foldEQ_utf8(const char *s1, char **pe1, UV l1,
                                           bool u1, const char *s2, char **pe2,
                                           UV l2, bool u2)

       is_ascii_string
               Returns true if the first "len" bytes of the string "s" are the same whether or not the string is
               encoded in UTF-8 (or UTF-EBCDIC on EBCDIC machines).  That is, if they are invariant.  On ASCII-ish
               machines, only ASCII characters fit this definition, hence the function's name.

               If "len" is 0, it will be calculated using strlen(s).

               See also "is_utf8_string"(), "is_utf8_string_loclen"(), and "is_utf8_string_loc"().

                       bool    is_ascii_string(const U8 *s, STRLEN len)

       is_utf8_char
               DEPRECATED!

               Tests if some arbitrary number of bytes begins in a valid UTF-8 character.  Note that an INVARIANT
               (i.e. ASCII on non-EBCDIC machines) character is a valid UTF-8 character.  The actual number of bytes
               in the UTF-8 character will be returned if it is valid, otherwise 0.

               This function is deprecated due to the possibility that malformed input could cause reading beyond the
               end of the input buffer.  Use "is_utf8_char_buf" instead.

                       STRLEN  is_utf8_char(const U8 *s)

       is_utf8_char_buf
               Returns the number of bytes that comprise the first UTF-8 encoded character in buffer "buf".
               "buf_end" should point to one position beyond the end of the buffer.  0 is returned if "buf" does not
               point to a complete, valid UTF-8 encoded character.

               Note that an INVARIANT character (i.e. ASCII on non-EBCDIC machines) is a valid UTF-8 character.

                       STRLEN  is_utf8_char_buf(const U8 *buf,
                                                const U8 *buf_end)

       is_utf8_string

               See also "is_utf8_string_loclen"() and "is_utf8_string"().

                       bool    is_utf8_string_loc(const U8 *s, STRLEN len,
                                                  const U8 **p)

       is_utf8_string_loclen
               Like "is_utf8_string"() but stores the location of the failure (in the case of "utf8ness failure") or
               the location "s"+"len" (in the case of "utf8ness success") in the "ep", and the number of UTF-8
               encoded characters in the "el".

               See also "is_utf8_string_loc"() and "is_utf8_string"().

                       bool    is_utf8_string_loclen(const U8 *s, STRLEN len,
                                                     const U8 **ep, STRLEN *el)

       pv_uni_display
               Build to the scalar "dsv" a displayable version of the string "spv", length "len", the displayable
               version being at most "pvlim" bytes long (if longer, the rest is truncated and "..." will be
               appended).

               The "flags" argument can have UNI_DISPLAY_ISPRINT set to display isPRINT()able characters as
               themselves, UNI_DISPLAY_BACKSLASH to display the \\[nrfta\\] as the backslashed versions (like '\n')
               (UNI_DISPLAY_BACKSLASH is preferred over UNI_DISPLAY_ISPRINT for \\).  UNI_DISPLAY_QQ (and its alias
               UNI_DISPLAY_REGEX) have both UNI_DISPLAY_BACKSLASH and UNI_DISPLAY_ISPRINT turned on.

               The pointer to the PV of the "dsv" is returned.

                       char*   pv_uni_display(SV *dsv, const U8 *spv,
                                              STRLEN len, STRLEN pvlim,
                                              UV flags)

       sv_cat_decode
               The encoding is assumed to be an Encode object, the PV of the ssv is assumed to be octets in that
               encoding and decoding the input starts from the position which (PV + *offset) pointed to.  The dsv
               will be concatenated the decoded UTF-8 string from ssv.  Decoding will terminate when the string tstr
               appears in decoding output or the input ends on the PV of the ssv.  The value which the offset points
               will be modified to the last input position on the ssv.

               Returns TRUE if the terminator was found, else returns FALSE.

                       bool    sv_cat_decode(SV* dsv, SV *encoding, SV *ssv,
                                             int *offset, char* tstr, int tlen)

       sv_recode_to_utf8
               The encoding is assumed to be an Encode object, on entry the PV of the sv is assumed to be octets in
               that encoding, and the sv will be converted into Unicode (and UTF-8).

               If the sv already is UTF-8 (or if it is not POK), or if the encoding is not a reference, nothing is
               done to the sv.  If the encoding is not an "Encode::XS" Encoding object, bad things will happen.  (See
               lib/encoding.pm and Encode.)

               The PV of the sv is returned.

                       char*   sv_recode_to_utf8(SV* sv, SV *encoding)

       to_utf8_case
               The "p" contains the pointer to the UTF-8 string encoding the character that is being converted.  This
               routine assumes that the character at "p" is well-formed.

               The "ustrp" is a pointer to the character buffer to put the conversion result to.  The "lenp" is a
               pointer to the length of the result.

               The "swashp" is a pointer to the swash to use.

               Both the special and normal mappings are stored in lib/unicore/To/Foo.pl, and loaded by SWASHNEW,
               using lib/utf8_heavy.pl.  The "special" (usually, but not always, a multicharacter mapping), is tried
               first.

               The "special" is a string like "utf8::ToSpecLower", which means the hash %utf8::ToSpecLower.  The
               access to the hash is through Perl_to_utf8_case().

               The "normal" is a string like "ToLower" which means the swash %utf8::ToLower.

                       UV      to_utf8_case(const U8 *p, U8* ustrp,
                                            STRLEN *lenp, SV **swashp,
                                            const char *normal,
                                            const char *special)

       to_utf8_fold
               Convert the UTF-8 encoded character at "p" to its foldcase version and store that in UTF-8 in "ustrp"
               and its length in bytes in "lenp".  Note that the "ustrp" needs to be at least UTF8_MAXBYTES_CASE+1
               bytes since the foldcase version may be longer than the original character (up to three characters).

               The first character of the foldcased version is returned (but note, as explained above, that there may
               be more.)

               The character at "p" is assumed by this routine to be well-formed.

                       UV      to_utf8_fold(const U8 *p, U8* ustrp,
                                            STRLEN *lenp)

       to_utf8_lower
               Convert the UTF-8 encoded character at "p" to its lowercase version and store that in UTF-8 in ustrp
               and its length in bytes in "lenp".  Note that the "ustrp" needs to be at least UTF8_MAXBYTES_CASE+1
               bytes since the lowercase version may be longer than the original character.

               The first character of the lowercased version is returned (but note, as explained above, that there
               may be more.)

               The character at "p" is assumed by this routine to be well-formed.

                       UV      to_utf8_lower(const U8 *p, U8* ustrp,
                                             STRLEN *lenp)

       to_utf8_title
               Convert the UTF-8 encoded character at "p" to its titlecase version and store that in UTF-8 in "ustrp"
               and its length in bytes in "lenp".  Note that the "ustrp" needs to be at least UTF8_MAXBYTES_CASE+1
               bytes since the titlecase version may be longer than the original character.


               The first character of the uppercased version is returned (but note, as explained above, that there
               may be more.)

               The character at "p" is assumed by this routine to be well-formed.

                       UV      to_utf8_upper(const U8 *p, U8* ustrp,
                                             STRLEN *lenp)

       utf8n_to_uvchr
               Returns the native character value of the first character in the string "s" which is assumed to be in
               UTF-8 encoding; "retlen" will be set to the length, in bytes, of that character.

               "length" and "flags" are the same as "utf8n_to_uvuni"().

                       UV      utf8n_to_uvchr(const U8 *s, STRLEN curlen,
                                              STRLEN *retlen, U32 flags)

       utf8n_to_uvuni
               Bottom level UTF-8 decode routine.  Returns the code point value of the first character in the string
               "s", which is assumed to be in UTF-8 (or UTF-EBCDIC) encoding, and no longer than "curlen" bytes;
               *retlen (if "retlen" isn't NULL) will be set to the length, in bytes, of that character.

               The value of "flags" determines the behavior when "s" does not point to a well-formed UTF-8 character.
               If "flags" is 0, when a malformation is found, zero is returned and *retlen is set so that
               ("s" + *retlen) is the next possible position in "s" that could begin a non-malformed character.
               Also, if UTF-8 warnings haven't been lexically disabled, a warning is raised.

               Various ALLOW flags can be set in "flags" to allow (and not warn on) individual types of
               malformations, such as the sequence being overlong (that is, when there is a shorter sequence that can
               express the same code point; overlong sequences are expressly forbidden in the UTF-8 standard due to
               potential security issues).  Another malformation example is the first byte of a character not being a
               legal first byte.  See utf8.h for the list of such flags.  For allowed 0 length strings, this function
               returns 0; for allowed overlong sequences, the computed code point is returned; for all other allowed
               malformations, the Unicode REPLACEMENT CHARACTER is returned, as these have no determinable reasonable
               value.

               The UTF8_CHECK_ONLY flag overrides the behavior when a non-allowed (by other flags) malformation is
               found.  If this flag is set, the routine assumes that the caller will raise a warning, and this
               function will silently just set "retlen" to "-1" and return zero.

               Certain code points are considered problematic.  These are Unicode surrogates, Unicode non-characters,
               and code points above the Unicode maximum of 0x10FFFF.  By default these are considered regular code
               points, but certain situations warrant special handling for them.  If "flags" contains
               UTF8_DISALLOW_ILLEGAL_INTERCHANGE, all three classes are treated as malformations and handled as such.
               The flags UTF8_DISALLOW_SURROGATE, UTF8_DISALLOW_NONCHAR, and UTF8_DISALLOW_SUPER (meaning above the
               legal Unicode maximum) can be set to disallow these categories individually.

               The flags UTF8_WARN_ILLEGAL_INTERCHANGE, UTF8_WARN_SURROGATE, UTF8_WARN_NONCHAR, and UTF8_WARN_SUPER
               will cause warning messages to be raised for their respective categories, but otherwise the code
               points are considered valid (not malformations).  To get a category to both be treated as a
               malformation and raise a warning, specify both the WARN and DISALLOW flags.  (But note that warnings
               are not raised if lexically disabled nor if UTF8_CHECK_ONLY is also specified.)

               All other code points corresponding to Unicode characters, including private use and those yet to be
               assigned, are never considered malformed and never warn.

               Most code should use "utf8_to_uvchr_buf"() rather than call this directly.

                       UV      utf8n_to_uvuni(const U8 *s, STRLEN curlen,
                                              STRLEN *retlen, U32 flags)

       utf8_distance
               Returns the number of UTF-8 characters between the UTF-8 pointers "a" and "b".

               WARNING: use only if you *know* that the pointers point inside the same UTF-8 buffer.

                       IV      utf8_distance(const U8 *a, const U8 *b)

       utf8_hop
               Return the UTF-8 pointer "s" displaced by "off" characters, either forward or backward.

               WARNING: do not use the following unless you *know* "off" is within the UTF-8 data pointed to by "s"
               *and* that on entry "s" is aligned on the first byte of character or just after the last byte of a
               character.

                       U8*     utf8_hop(const U8 *s, I32 off)

       utf8_length
               Return the length of the UTF-8 char encoded string "s" in characters.  Stops at "e" (inclusive).  If
               "e < s" or if the scan would end up past "e", croaks.

                       STRLEN  utf8_length(const U8* s, const U8 *e)

       utf8_to_bytes
               Converts a string "s" of length "len" from UTF-8 into native byte encoding.  Unlike "bytes_to_utf8",
               this over-writes the original string, and updates "len" to contain the new length.  Returns zero on
               failure, setting "len" to -1.

               If you need a copy of the string, see "bytes_from_utf8".

               NOTE: this function is experimental and may change or be removed without notice.

                       U8*     utf8_to_bytes(U8 *s, STRLEN *len)

       utf8_to_uvchr
               DEPRECATED!

               Returns the native code point of the first character in the string "s" which is assumed to be in UTF-8
               encoding; "retlen" will be set to the length, in bytes, of that character.

               Some, but not all, UTF-8 malformations are detected, and in fact, some malformed input could cause
               reading beyond the end of the input buffer, which is why this function is deprecated.  Use
               "utf8_to_uvchr_buf" instead.

               If "s" points to one of the detected malformations, and UTF8 warnings are enabled, zero is returned
               and *retlen is set (if "retlen" isn't NULL) to -1.  If those warnings are off, the computed value if
               well-defined (or the Unicode REPLACEMENT CHARACTER, if not) is silently returned, and *retlen is set
               and *retlen is set (if "retlen" isn't NULL) to -1.  If those warnings are off, the computed value if
               well-defined (or the Unicode REPLACEMENT CHARACTER, if not) is silently returned, and *retlen is set
               (if "retlen" isn't NULL) so that ("s" + *retlen) is the next possible position in "s" that could begin
               a non-malformed character.  See "utf8n_to_uvuni" for details on when the REPLACEMENT CHARACTER is
               returned.

                       UV      utf8_to_uvchr_buf(const U8 *s, const U8 *send,
                                                 STRLEN *retlen)

       utf8_to_uvuni
               DEPRECATED!

               Returns the Unicode code point of the first character in the string "s" which is assumed to be in
               UTF-8 encoding; "retlen" will be set to the length, in bytes, of that character.

               This function should only be used when the returned UV is considered an index into the Unicode
               semantic tables (e.g. swashes).

               Some, but not all, UTF-8 malformations are detected, and in fact, some malformed input could cause
               reading beyond the end of the input buffer, which is why this function is deprecated.  Use
               "utf8_to_uvuni_buf" instead.

               If "s" points to one of the detected malformations, and UTF8 warnings are enabled, zero is returned
               and *retlen is set (if "retlen" doesn't point to NULL) to -1.  If those warnings are off, the computed
               value if well-defined (or the Unicode REPLACEMENT CHARACTER, if not) is silently returned, and *retlen
               is set (if "retlen" isn't NULL) so that ("s" + *retlen) is the next possible position in "s" that
               could begin a non-malformed character.  See "utf8n_to_uvuni" for details on when the REPLACEMENT
               CHARACTER is returned.

                       UV      utf8_to_uvuni(const U8 *s, STRLEN *retlen)

       utf8_to_uvuni_buf
               Returns the Unicode code point of the first character in the string "s" which is assumed to be in
               UTF-8 encoding; "send" points to 1 beyond the end of "s".  "retlen" will be set to the length, in
               bytes, of that character.

               This function should only be used when the returned UV is considered an index into the Unicode
               semantic tables (e.g. swashes).

               If "s" does not point to a well-formed UTF-8 character and UTF8 warnings are enabled, zero is returned
               and *retlen is set (if "retlen" isn't NULL) to -1.  If those warnings are off, the computed value if
               well-defined (or the Unicode REPLACEMENT CHARACTER, if not) is silently returned, and *retlen is set
               (if "retlen" isn't NULL) so that ("s" + *retlen) is the next possible position in "s" that could begin
               a non-malformed character.  See "utf8n_to_uvuni" for details on when the REPLACEMENT CHARACTER is
               returned.

                       UV      utf8_to_uvuni_buf(const U8 *s, const U8 *send,
                                                 STRLEN *retlen)

       uvchr_to_utf8
               Adds the UTF-8 representation of the Native code point "uv" to the end of the string "d"; "d" should
               have at least "UTF8_MAXBYTES+1" free bytes available. The return value is the pointer to the byte
               after the end of the new character. In other words,


                   d = uvuni_to_utf8_flags(d, uv, flags);

               or, in most cases,

                   d = uvuni_to_utf8(d, uv);

               (which is equivalent to)

                   d = uvuni_to_utf8_flags(d, uv, 0);

               This is the recommended Unicode-aware way of saying

                   *(d++) = uv;

               This function will convert to UTF-8 (and not warn) even code points that aren't legal Unicode or are
               problematic, unless "flags" contains one or more of the following flags:

               If "uv" is a Unicode surrogate code point and UNICODE_WARN_SURROGATE is set, the function will raise a
               warning, provided UTF8 warnings are enabled.  If instead UNICODE_DISALLOW_SURROGATE is set, the
               function will fail and return NULL.  If both flags are set, the function will both warn and return
               NULL.

               The UNICODE_WARN_NONCHAR and UNICODE_DISALLOW_NONCHAR flags correspondingly affect how the function
               handles a Unicode non-character.  And, likewise for the UNICODE_WARN_SUPER and UNICODE_DISALLOW_SUPER
               flags, and code points that are above the Unicode maximum of 0x10FFFF.  Code points above 0x7FFF_FFFF
               (which are even less portable) can be warned and/or disallowed even if other above-Unicode code points
               are accepted by the UNICODE_WARN_FE_FF and UNICODE_DISALLOW_FE_FF flags.

               And finally, the flag UNICODE_WARN_ILLEGAL_INTERCHANGE selects all four of the above WARN flags; and
               UNICODE_DISALLOW_ILLEGAL_INTERCHANGE selects all four DISALLOW flags.

                       U8*     uvuni_to_utf8_flags(U8 *d, UV uv, UV flags)

Variables created by "xsubpp" and "xsubpp" internal functions
       ax      Variable which is setup by "xsubpp" to indicate the stack base offset, used by the "ST", "XSprePUSH"
               and "XSRETURN" macros.  The "dMARK" macro must be called prior to setup the "MARK" variable.

                       I32     ax

       CLASS   Variable which is setup by "xsubpp" to indicate the class name for a C++ XS constructor.  This is
               always a "char*".  See "THIS".

                       char*   CLASS

       dAX     Sets up the "ax" variable.  This is usually handled automatically by "xsubpp" by calling "dXSARGS".

                               dAX;

       dAXMARK Sets up the "ax" variable and stack marker variable "mark".  This is usually handled automatically by
               "xsubpp" by calling "dXSARGS".

                               dAXMARK;


               variables by calling "dAX" and "dITEMS".  This is usually handled automatically by "xsubpp".

                               dXSARGS;

       dXSI32  Sets up the "ix" variable for an XSUB which has aliases.  This is usually handled automatically by
               "xsubpp".

                               dXSI32;

       items   Variable which is setup by "xsubpp" to indicate the number of items on the stack.  See "Variable-
               length Parameter Lists" in perlxs.

                       I32     items

       ix      Variable which is setup by "xsubpp" to indicate which of an XSUB's aliases was used to invoke it.  See
               "The ALIAS: Keyword" in perlxs.

                       I32     ix

       newXSproto
               Used by "xsubpp" to hook up XSUBs as Perl subs.  Adds Perl prototypes to the subs.

       RETVAL  Variable which is setup by "xsubpp" to hold the return value for an XSUB. This is always the proper
               type for the XSUB. See "The RETVAL Variable" in perlxs.

                       (whatever)      RETVAL

       ST      Used to access elements on the XSUB's stack.

                       SV*     ST(int ix)

       THIS    Variable which is setup by "xsubpp" to designate the object in a C++ XSUB.  This is always the proper
               type for the C++ object.  See "CLASS" and "Using XS With C++" in perlxs.

                       (whatever)      THIS

       UNDERBAR
               The SV* corresponding to the $_ variable. Works even if there is a lexical $_ in scope.

       XS      Macro to declare an XSUB and its C parameter list.  This is handled by "xsubpp". It is the same as
               using the more explicit XS_EXTERNAL macro.

       XS_APIVERSION_BOOTCHECK
               Macro to verify that the perl api version an XS module has been compiled against matches the api
               version of the perl interpreter it's being loaded into.

                               XS_APIVERSION_BOOTCHECK;

       XS_EXTERNAL
               Macro to declare an XSUB and its C parameter list explicitly exporting the symbols.

       XS_INTERNAL
               Macro to declare an XSUB and its C parameter list without exporting the symbols.  This is handled by
               "xsubpp" and generally preferable over exporting the XSUB symbols unnecessarily.

       croak   This is an XS interface to Perl's "die" function.

               Take a sprintf-style format pattern and argument list.  These are used to generate a string message.
               If the message does not end with a newline, then it will be extended with some indication of the
               current location in the code, as described for "mess_sv".

               The error message will be used as an exception, by default returning control to the nearest enclosing
               "eval", but subject to modification by a $SIG{__DIE__} handler.  In any case, the "croak" function
               never returns normally.

               For historical reasons, if "pat" is null then the contents of "ERRSV" ($@) will be used as an error
               message or object instead of building an error message from arguments.  If you want to throw a non-
               string object, or build an error message in an SV yourself, it is preferable to use the "croak_sv"
               function, which does not involve clobbering "ERRSV".

                       void    croak(const char *pat, ...)

       croak_no_modify
               Exactly equivalent to "Perl_croak(aTHX_ "%s", PL_no_modify)", but generates terser object code than
               using "Perl_croak". Less code used on exception code paths reduces CPU cache pressure.

                       void    croak_no_modify()

       croak_sv
               This is an XS interface to Perl's "die" function.

               "baseex" is the error message or object.  If it is a reference, it will be used as-is.  Otherwise it
               is used as a string, and if it does not end with a newline then it will be extended with some
               indication of the current location in the code, as described for "mess_sv".

               The error message or object will be used as an exception, by default returning control to the nearest
               enclosing "eval", but subject to modification by a $SIG{__DIE__} handler.  In any case, the "croak_sv"
               function never returns normally.

               To die with a simple string message, the "croak" function may be more convenient.

                       void    croak_sv(SV *baseex)

       die     Behaves the same as "croak", except for the return type.  It should be used only where the "OP *"
               return type is required.  The function never actually returns.

                       OP *    die(const char *pat, ...)

       die_sv  Behaves the same as "croak_sv", except for the return type.  It should be used only where the "OP *"
               return type is required.  The function never actually returns.

                       OP *    die_sv(SV *baseex)

       vcroak  This is an XS interface to Perl's "die" function.

               "pat" and "args" are a sprintf-style format pattern and encapsulated argument list.  These are used to
               generate a string message.  If the message does not end with a newline, then it will be extended with
               some indication of the current location in the code, as described for "mess_sv".


               "pat" and "args" are a sprintf-style format pattern and encapsulated argument list.  These are used to
               generate a string message.  If the message does not end with a newline, then it will be extended with
               some indication of the current location in the code, as described for "mess_sv".

               The error message or object will by default be written to standard error, but this is subject to
               modification by a $SIG{__WARN__} handler.

               Unlike with "vcroak", "pat" is not permitted to be null.

                       void    vwarn(const char *pat, va_list *args)

       warn    This is an XS interface to Perl's "warn" function.

               Take a sprintf-style format pattern and argument list.  These are used to generate a string message.
               If the message does not end with a newline, then it will be extended with some indication of the
               current location in the code, as described for "mess_sv".

               The error message or object will by default be written to standard error, but this is subject to
               modification by a $SIG{__WARN__} handler.

               Unlike with "croak", "pat" is not permitted to be null.

                       void    warn(const char *pat, ...)

       warn_sv This is an XS interface to Perl's "warn" function.

               "baseex" is the error message or object.  If it is a reference, it will be used as-is.  Otherwise it
               is used as a string, and if it does not end with a newline then it will be extended with some
               indication of the current location in the code, as described for "mess_sv".

               The error message or object will by default be written to standard error, but this is subject to
               modification by a $SIG{__WARN__} handler.

               To warn with a simple string message, the "warn" function may be more convenient.

                       void    warn_sv(SV *baseex)

Undocumented functions
       The following functions have been flagged as part of the public API, but are currently undocumented. Use them
       at your own risk, as the interfaces are subject to change.

       If you use one of them, you may wish to consider creating and submitting documentation for it. If your patch
       is accepted, this will indicate that the interface is stable (unless it is explicitly marked otherwise).

       GetVars
       Gv_AMupdate
       PerlIO_clearerr
       PerlIO_close
       PerlIO_context_layers
       PerlIO_eof
       PerlIO_error
       PerlIO_fileno
       PerlIO_fill
       PerlIO_stdout
       PerlIO_tell
       PerlIO_unread
       PerlIO_write
       Slab_Alloc
       Slab_Free
       _is_utf8_quotemeta
       amagic_call
       amagic_deref_call
       any_dup
       atfork_lock
       atfork_unlock
       av_arylen_p
       av_iter_p
       block_gimme
       call_atexit
       call_list
       calloc
       cast_i32
       cast_iv
       cast_ulong
       cast_uv
       ck_warner
       ck_warner_d
       ckwarn
       ckwarn_d
       clone_params_del
       clone_params_new
       croak_nocontext
       csighandler
       cx_dump
       cx_dup
       cxinc
       deb
       deb_nocontext
       debop
       debprofdump
       debstack
       debstackptrs
       delimcpy
       despatch_signals
       die_nocontext
       dirp_dup
       do_aspawn
       do_binmode
       do_close
       do_gv_dump
       do_gvgv_dump
       do_hv_dump
       do_join
       do_magic_dump
       do_op_dump
       do_open
       do_open9
       dump_fds
       dump_form
       dump_indent
       dump_mstats
       dump_packsubs
       dump_sub
       dump_vindent
       filter_add
       filter_del
       filter_read
       foldEQ_latin1
       form_nocontext
       fp_dup
       fprintf_nocontext
       free_global_struct
       free_tmps
       get_context
       get_mstats
       get_op_descs
       get_op_names
       get_ppaddr
       get_vtbl
       gp_dup
       gp_free
       gp_ref
       gv_AVadd
       gv_HVadd
       gv_IOadd
       gv_SVadd
       gv_add_by_type
       gv_autoload4
       gv_autoload_pv
       gv_autoload_pvn
       gv_autoload_sv
       gv_check
       gv_dump
       gv_efullname
       gv_efullname3
       gv_efullname4
       gv_fetchfile
       gv_fetchfile_flags
       gv_fetchpv
       gv_fetchpvn_flags
       gv_fetchsv
       gv_fullname
       gv_fullname3
       gv_fullname4
       gv_handler
       gv_name_set
       he_dup
       hek_dup
       hv_common
       hv_common_key_len
       hv_delayfree_ent
       init_i18nl14n
       init_stacks
       init_tm
       instr
       is_lvalue_sub
       is_uni_alnum
       is_uni_alnum_lc
       is_uni_alpha
       is_uni_alpha_lc
       is_uni_ascii
       is_uni_ascii_lc
       is_uni_cntrl
       is_uni_cntrl_lc
       is_uni_digit
       is_uni_digit_lc
       is_uni_graph
       is_uni_graph_lc
       is_uni_idfirst
       is_uni_idfirst_lc
       is_uni_lower
       is_uni_lower_lc
       is_uni_print
       is_uni_print_lc
       is_uni_punct
       is_uni_punct_lc
       is_uni_space
       is_uni_space_lc
       is_uni_upper
       is_uni_upper_lc
       is_uni_xdigit
       is_uni_xdigit_lc
       is_utf8_alnum
       is_utf8_alpha
       is_utf8_ascii
       is_utf8_cntrl
       is_utf8_digit
       is_utf8_graph
       is_utf8_idcont
       is_utf8_idfirst
       is_utf8_lower
       is_utf8_mark
       is_utf8_perl_space
       is_utf8_perl_word
       is_utf8_posix_digit
       is_utf8_print
       is_utf8_punct
       is_utf8_space
       is_utf8_upper
       is_utf8_xdigit
       is_utf8_xidcont
       is_utf8_xidfirst
       leave_scope
       load_module_nocontext
       magic_dump
       my_atof
       my_atof2
       my_bcopy
       my_bzero
       my_chsize
       my_cxt_index
       my_cxt_init
       my_dirfd
       my_exit
       my_failure_exit
       my_fflush_all
       my_fork
       my_htonl
       my_lstat
       my_memcmp
       my_memset
       my_ntohl
       my_pclose
       my_popen
       my_popen_list
       my_setenv
       my_socketpair
       my_stat
       my_strftime
       my_strlcat
       my_strlcpy
       my_swap
       newANONATTRSUB
       newANONHASH
       newANONLIST
       newANONSUB
       newATTRSUB
       newAVREF
       newCVREF
       newFORM
       newGVREF
       newGVgen
       newGVgen_flags
       newHVREF
       newHVhv
       newIO
       newMYSUB
       newPROG
       newRV
       newSUB
       newSVREF
       newSVpvf_nocontext
       new_collate
       new_ctype
       new_numeric
       new_stackinfo
       ninstr
       op_dump
       op_free
       printf_nocontext
       ptr_table_clear
       ptr_table_fetch
       ptr_table_free
       ptr_table_new
       ptr_table_split
       ptr_table_store
       push_scope
       re_compile
       re_dup_guts
       re_intuit_start
       re_intuit_string
       realloc
       reentrant_free
       reentrant_init
       reentrant_retry
       reentrant_size
       ref
       reg_named_buff_all
       reg_named_buff_exists
       reg_named_buff_fetch
       reg_named_buff_firstkey
       reg_named_buff_nextkey
       reg_named_buff_scalar
       regclass_swash
       regdump
       regdupe_internal
       regexec_flags
       regfree_internal
       reginitcolors
       regnext
       repeatcpy
       rninstr
       rsignal
       rsignal_state
       runops_debug
       runops_standard
       rvpv_dup
       safesyscalloc
       safesysfree
       safesysmalloc
       safesysrealloc
       save_I16
       save_I32
       save_I8
       save_adelete
       save_aelem
       save_aelem_flags
       save_alloc
       save_aptr
       save_ary
       save_bool
       save_clearsv
       save_delete
       save_hints
       save_hptr
       save_int
       save_item
       save_iv
       save_list
       save_long
       save_mortalizesv
       save_nogv
       save_op
       save_padsv_and_mortalize
       save_pptr
       save_pushi32ptr
       save_pushptr
       save_pushptrptr
       save_re_context
       save_scalar
       save_set_svflags
       save_shared_pvref
       save_sptr
       save_svref
       save_vptr
       savestack_grow
       savestack_grow_cnt
       scan_num
       scan_vstring
       screaminstr
       seed
       set_context
       set_numeric_local
       set_numeric_radix
       set_numeric_standard
       share_hek
       si_dup
       ss_dup
       stack_grow
       start_subparse
       stashpv_hvname_match
       str_to_version
       sv_2iv
       sv_2pv
       sv_2uv
       sv_catpvf_mg_nocontext
       sv_catpvf_nocontext
       sv_compile_2op
       sv_dump
       sv_dup
       sv_dup_inc
       sv_peek
       sv_pvn_nomg
       sv_setpvf_mg_nocontext
       sv_setpvf_nocontext
       sv_utf8_upgrade_flags_grow
       swash_fetch
       to_uni_lower_lc
       to_uni_title
       to_uni_title_lc
       to_uni_upper
       to_uni_upper_lc
       unlnk
       unsharepvn
       utf16_to_utf8
       utf16_to_utf8_reversed
       uvchr_to_utf8_flags
       uvuni_to_utf8
       vdeb
       vform
       vload_module
       vnewSVpvf
       vwarner
       warn_nocontext
       warner
       warner_nocontext
       whichsig
       whichsig_pv
       whichsig_pvn
       whichsig_sv

AUTHORS
       Until May 1997, this document was maintained by Jeff Okamoto <[email protected]>.  It is now maintained as
       part of Perl itself.

       With lots of help and suggestions from Dean Roehrich, Malcolm Beattie, Andreas Koenig, Paul Hudson, Ilya
       Zakharevich, Paul Marquess, Neil Bowers, Matthew Green, Tim Bunce, Spider Boardman, Ulrich Pfeifer, Stephen
       McCamant, and Gurusamy Sarathy.

       API Listing originally by Dean Roehrich <[email protected]>.

       Updated to be autogenerated from comments in the source by Benjamin Stuhl.

SEE ALSO
       perlguts, perlxs, perlxstut, perlintern



perl v5.16.3                                          2016-11-06                                           PERLAPI(1)