perlintern - autogenerated documentation of purely internal Perl functions
This file is the autogenerated documentation of functions in the Perl interpreter that are documented using Perl's internal documentation format but are not marked as part of the Perl API. In other words, they are not for use in extensions!
Return an entry from the BHK structure. which is a preprocessor token indicating which entry to return. If the appropriate flag is not set this will return NULL. The type of the return value depends on which entry you ask for.
NOTE: this function is experimental and may change or be removed without notice.
void * BhkENTRY(BHK *hk, which)Return the BHK's flags.
NOTE: this function is experimental and may change or be removed without notice.
U32 BhkFLAGS(BHK *hk)Call all the registered block hooks for type which. which is a preprocessing token; the type of arg depends on which.
NOTE: this function is experimental and may change or be removed without notice.
void CALL_BLOCK_HOOKS(which, arg)Each CV has a pointer, CvOUTSIDE(), to its lexically enclosing CV (if any). Because pointers to anonymous sub prototypes are stored in & pad slots, it is a possible to get a circular reference, with the parent pointing to the child and vice-versa. To avoid the ensuing memory leak, we do not increment the reference count of the CV pointed to by CvOUTSIDE in the one specific instance that the parent has a & pad slot pointing back to us. In this case, we set the CvWEAKOUTSIDE flag in the child. This allows us to determine under what circumstances we should decrement the refcount of the parent when freeing the child.
There is a further complication with non-closure anonymous subs (i.e. those that do not refer to any lexicals outside that sub). In this case, the anonymous prototype is shared rather than being cloned. This has the consequence that the parent may be freed while there are still active children, eg
BEGIN { $a = sub { eval '$x' } }In this case, the BEGIN is freed immediately after execution since there are no active references to it: the anon sub prototype has CvWEAKOUTSIDE set since it's not a closure, and $a points to the same CV, so it doesn't contribute to BEGIN's refcount either. When $a is executed, the eval '$x' causes the chain of CvOUTSIDEs to be followed, and the freed BEGIN is accessed.
To avoid this, whenever a CV and its associated pad is freed, any & entries in the pad are explicitly removed from the pad, and if the refcount of the pointed-to anon sub is still positive, then that child's CvOUTSIDE is set to point to its grandparent. This will only occur in the single specific case of a non-closure anon prototype having one or more active references (such as $a above).
One other thing to consider is that a CV may be merely undefined rather than freed, eg undef &foo. In this case, its refcount may not have reached zero, but we still delete its pad and its CvROOT etc. Since various children may still have their CvOUTSIDE pointing at this undefined CV, we keep its own CvOUTSIDE for the time being, so that the chain of lexical scopes is unbroken. For example, the following should print 123:
my $x = 123;
sub tmp { sub { eval '$x' } }
my $a = tmp();
undef &tmp;
print $a->();
bool CvWEAKOUTSIDE(CV *cv)Clone a CV: make a new CV which points to the same code etc, but which has a newly-created pad built by copying the prototype pad and capturing any outer lexicals.
CV* cv_clone(CV* proto)dump the contents of a CV
void cv_dump(const CV *cv, const char *title)Dump the contents of a padlist
void do_dump_pad(I32 level, PerlIO *file, PADLIST *padlist, int full)"Introduce" my variables to visible status.
U32 intro_my()Add an anon code entry to the current compiling pad
PADOFFSET pad_add_anon(SV* sv, OPCODE op_type)Create a new name and associated PADMY SV in the current pad; return the offset. If typestash is valid, the name is for a typed lexical; set the name's stash to that value. If ourstash is valid, it's an our lexical, set the name's SvOURSTASH to that value
If fake, it means we're cloning an existing entry
NOTE: this function is experimental and may change or be removed without notice.
PADOFFSET pad_add_name(const char *name, const STRLEN len, const U32 flags, HV *typestash, HV *ourstash)Allocate a new my or tmp pad entry. For a my, simply push a null SV onto the end of PL_comppad, but for a tmp, scan the pad from PL_padix upwards for a slot which has no name and no active value.
PADOFFSET pad_alloc(I32 optype, U32 tmptype)Update the pad compilation state variables on entry to a new block
void pad_block_start(int full)Check for duplicate declarations: report any of: * a my in the current scope with the same name; * an our (anywhere in the pad) with the same name and the same stash as ourstash is_our indicates that the name to check is an 'our' declaration
void pad_check_dup(SV *name, const U32 flags, const HV *ourstash)Find a named lexical anywhere in a chain of nested pads. Add fake entries in the inner pads if it's found in an outer one.
Returns the offset in the bottom pad of the lex or the fake lex. cv is the CV in which to start the search, and seq is the current cop_seq to match against. If warn is true, print appropriate warnings. The out_* vars return values, and so are pointers to where the returned values should be stored. out_capture, if non-null, requests that the innermost instance of the lexical is captured; out_name_sv is set to the innermost matched namesv or fake namesv; out_flags returns the flags normally associated with the IVX field of a fake namesv.
Note that pad_findlex() is recursive; it recurses up the chain of CVs, then comes back down, adding fake entries as it goes. It has to be this way because fake namesvs in anon protoypes have to store in xlow the index into the parent pad.
PADOFFSET pad_findlex(const char *name, const CV* cv, U32 seq, int warn, SV** out_capture, SV** out_name_sv, int *out_flags)For any anon CVs in the pad, change CvOUTSIDE of that CV from old_cv to new_cv if necessary. Needed when a newly-compiled CV has to be moved to a pre-existing CV struct.
void pad_fixup_inner_anons(PADLIST *padlist, CV *old_cv, CV *new_cv)Free the SV at offset po in the current pad.
void pad_free(PADOFFSET po)Cleanup at end of scope during compilation: set the max seq number for lexicals in this scope and warn of any lexicals that never got introduced.
void pad_leavemy()Push a new pad frame onto the padlist, unless there's already a pad at this depth, in which case don't bother creating a new one. Then give the new pad an @_ in slot zero.
void pad_push(PADLIST *padlist, int depth)Mark all the current temporaries for reuse
void pad_reset()Set the entry at offset po in the current pad to sv. Use the macro PAD_SETSV() rather than calling this function directly.
void pad_setsv(PADOFFSET po, SV* sv)Abandon the tmp in the current pad at offset po and replace with a new one.
void pad_swipe(PADOFFSET po, bool refadjust)Tidy up a pad after we've finished compiling it: * remove most stuff from the pads of anonsub prototypes; * give it a @_; * mark tmps as such.
void pad_tidy(padtidy_type type)Save the current pad in the given context block structure.
void CX_CURPAD_SAVE(struct context)Access the SV at offset po in the saved current pad in the given context block structure (can be used as an lvalue).
SV * CX_CURPAD_SV(struct context, PADOFFSET po)Get the value from slot po in the base (DEPTH=1) pad of a padlist
SV * PAD_BASE_SV(PADLIST padlist, PADOFFSET po)Clone the state variables associated with running and compiling pads.
void PAD_CLONE_VARS(PerlInterpreter *proto_perl, CLONE_PARAMS* param)Return the flags for the current compiling pad name at offset po. Assumes a valid slot entry.
U32 PAD_COMPNAME_FLAGS(PADOFFSET po)The generation number of the name at offset po in the current compiling pad (lvalue). Note that SvUVX is hijacked for this purpose.
STRLEN PAD_COMPNAME_GEN(PADOFFSET po)Sets the generation number of the name at offset po in the current ling pad (lvalue) to gen. Note that SvUV_set is hijacked for this purpose.
STRLEN PAD_COMPNAME_GEN_set(PADOFFSET po, int gen)Return the stash associated with an our variable. Assumes the slot entry is a valid our lexical.
HV * PAD_COMPNAME_OURSTASH(PADOFFSET po)Return the name of the current compiling pad name at offset po. Assumes a valid slot entry.
char * PAD_COMPNAME_PV(PADOFFSET po)Return the type (stash) of the current compiling pad name at offset po. Must be a valid name. Returns null if not typed.
HV * PAD_COMPNAME_TYPE(PADOFFSET po)Clone a padlist.
void PAD_DUP(PADLIST dstpad, PADLIST srcpad, CLONE_PARAMS* param)Restore the old pad saved into the local variable opad by PAD_SAVE_LOCAL()
void PAD_RESTORE_LOCAL(PAD *opad)Save the current pad to the local variable opad, then make the current pad equal to npad
void PAD_SAVE_LOCAL(PAD *opad, PAD *npad)Save the current pad then set it to null.
void PAD_SAVE_SETNULLPAD()Set the slot at offset po in the current pad to sv
SV * PAD_SETSV(PADOFFSET po, SV* sv)Set the current pad to be pad n in the padlist, saving the previous current pad. NB currently this macro expands to a string too long for some compilers, so it's best to replace it with
SAVECOMPPAD();
PAD_SET_CUR_NOSAVE(padlist,n);
void PAD_SET_CUR(PADLIST padlist, I32 n)like PAD_SET_CUR, but without the save
void PAD_SET_CUR_NOSAVE(PADLIST padlist, I32 n)Get the value at offset po in the current pad
void PAD_SV(PADOFFSET po)Lightweight and lvalue version of PAD_SV. Get or set the value at offset po in the current pad. Unlike PAD_SV, does not print diagnostics with -DX. For internal use only.
SV * PAD_SVl(PADOFFSET po)Clear the pointed to pad value on scope exit. (i.e. the runtime action of 'my')
void SAVECLEARSV(SV **svp)save PL_comppad and PL_curpad
void SAVECOMPPAD()Save a pad slot (used to restore after an iteration)
XXX DAPM it would make more sense to make the arg a PADOFFSET void SAVEPADSV(PADOFFSET po)
Check for the cases 0 or 3 of cur_env.je_ret, only used inside an eval context.
0 is used as continue inside eval,
3 is used for a die caught by an inner eval - continue inner loop
See cop.h: je_mustcatch, when set at any runlevel to TRUE, means eval ops must establish a local jmpenv to handle exception traps.
OP* docatch(OP *o)If the typeglob gv can be expressed more succinctly, by having something other than a real GV in its place in the stash, replace it with the optimised form. Basic requirements for this are that gv is a real typeglob, is sufficiently ordinary, and is only referenced from its package. This function is meant to be used when a GV has been looked up in part to see what was there, causing upgrading, but based on what was found it turns out that the real GV isn't required after all.
If gv is a completely empty typeglob, it is deleted from the stash.
If gv is a typeglob containing only a sufficiently-ordinary constant sub, the typeglob is replaced with a scalar-reference placeholder that more compactly represents the same thing.
NOTE: this function is experimental and may change or be removed without notice.
void gv_try_downgrade(GV* gv)Returns TRUE if given the name of a magical GV.
Currently only useful internally when determining if a GV should be created even in rvalue contexts.
flags is not used at present but available for future extension to allow selecting particular classes of magical variable.
Currently assumes that name is NUL terminated (as well as len being valid). This assumption is met by all callers within the perl core, which all pass pointers returned by SvPV.
bool is_gv_magical_sv(SV *const name_sv, U32 flags)Adds a name to a stash's internal list of effective names. See hv_ename_delete.
This is called when a stash is assigned to a new location in the symbol table.
void hv_ename_add(HV *hv, const char *name, U32 len, U32 flags)Removes a name from a stash's internal list of effective names. If this is the name returned by HvENAME, then another name in the list will take its place (HvENAME will use it).
This is called when a stash is deleted from the symbol table.
void hv_ename_delete(HV *hv, const char *name, U32 len, U32 flags)Generates and returns a HV * representing the content of a refcounted_he chain. flags is currently unused and must be zero.
HV * refcounted_he_chain_2hv(const struct refcounted_he *c, U32 flags)Like "refcounted_he_fetch_pvn", but takes a nul-terminated string instead of a string/length pair.
SV * refcounted_he_fetch_pv(const struct refcounted_he *chain, const char *key, U32 hash, U32 flags)Search along a refcounted_he chain for an entry with the key specified by keypv and keylen. If flags has the REFCOUNTED_HE_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 representing the value associated with the key, or &PL_sv_placeholder if there is no value associated with the key.
SV * refcounted_he_fetch_pvn(const struct refcounted_he *chain, const char *keypv, STRLEN keylen, U32 hash, U32 flags)Like "refcounted_he_fetch_pvn", but takes a literal string instead of a string/length pair, and no precomputed hash.
SV * refcounted_he_fetch_pvs(const struct refcounted_he *chain, const char *key, U32 flags)Like "refcounted_he_fetch_pvn", but takes a Perl scalar instead of a string/length pair.
SV * refcounted_he_fetch_sv(const struct refcounted_he *chain, SV *key, U32 hash, U32 flags)Decrements the reference count of a refcounted_he by one. If the reference count reaches zero the structure's memory is freed, which (recursively) causes a reduction of its parent refcounted_he's reference count. It is safe to pass a null pointer to this function: no action occurs in this case.
void refcounted_he_free(struct refcounted_he *he)Increment the reference count of a refcounted_he. The pointer to the refcounted_he is also returned. It is safe to pass a null pointer to this function: no action occurs and a null pointer is returned.
struct refcounted_he * refcounted_he_inc(struct refcounted_he *he)Like "refcounted_he_new_pvn", but takes a nul-terminated string instead of a string/length pair.
struct refcounted_he * refcounted_he_new_pv(struct refcounted_he *parent, const char *key, U32 hash, SV *value, U32 flags)Creates a new refcounted_he. This consists of a single key/value pair and a reference to an existing refcounted_he chain (which may be empty), and thus forms a longer chain. When using the longer chain, the new key/value pair takes precedence over any entry for the same key further along the chain.
The new key is specified by keypv and keylen. If flags has the REFCOUNTED_HE_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 refcounted_he. Complex types of scalar will not be stored with referential integrity, but will be coerced to strings. value may be either null or &PL_sv_placeholder to indicate that no value is to be associated with the key; this, as with any non-null value, takes precedence over the existence of a value for the key further along the chain.
parent points to the rest of the refcounted_he chain to be attached to the new refcounted_he. This function takes ownership of one reference to parent, and returns one reference to the new refcounted_he.
struct refcounted_he * refcounted_he_new_pvn(struct refcounted_he *parent, const char *keypv, STRLEN keylen, U32 hash, SV *value, U32 flags)Like "refcounted_he_new_pvn", but takes a literal string instead of a string/length pair, and no precomputed hash.
struct refcounted_he * refcounted_he_new_pvs(struct refcounted_he *parent, const char *key, SV *value, U32 flags)Like "refcounted_he_new_pvn", but takes a Perl scalar instead of a string/length pair.
struct refcounted_he * refcounted_he_new_sv(struct refcounted_he *parent, SV *key, U32 hash, SV *value, U32 flags)Function called by do_readline to spawn a glob (or do the glob inside perl on VMS). This code used to be inline, but now perl uses File::Glob this glob starter is only used by miniperl during the build process. Moving it away shrinks pp_hot.c; shrinking pp_hot.c helps speed perl up.
NOTE: this function is experimental and may change or be removed without notice.
PerlIO* start_glob(SV *tmpglob, IO *io)Triggered by a delete from %^H, records the key to PL_compiling.cop_hints_hash.
int magic_clearhint(SV* sv, MAGIC* mg)Triggered by clearing %^H, resets PL_compiling.cop_hints_hash.
int magic_clearhints(SV* sv, MAGIC* mg)Invoke a magic method (like FETCH).
* sv and mg are the tied thingy and the tie magic; * meth is the name of the method to call; * argc is the number of args (in addition to $self) to pass to the method; the args themselves are any values following the argc argument. * flags: G_DISCARD: invoke method with G_DISCARD flag and don't return a value G_UNDEF_FILL: fill the stack with argc pointers to PL_sv_undef.
Returns the SV (if any) returned by the method, or NULL on failure.
SV* magic_methcall(SV *sv, const MAGIC *mg, const char *meth, U32 flags, U32 argc, ...)Triggered by a store to %^H, records the key/value pair to PL_compiling.cop_hints_hash. It is assumed that hints aren't storing anything that would need a deep copy. Maybe we should warn if we find a reference.
int magic_sethint(SV* sv, MAGIC* mg)Copy some of the magic from an existing SV to new localized version of that SV. Container magic (eg %ENV, $1, tie) gets copied, value magic doesn't (eg taint, pos).
If setmagic is false then no set magic will be called on the new (empty) SV. This typically means that assignment will soon follow (e.g. 'local $x = $y'), and that will handle the magic.
void mg_localize(SV* sv, SV* nsv, bool setmagic)Returns the Depth-First Search linearization of @ISA the given stash. The return value is a read-only AV*. level should be 0 (it is used internally in this function's recursion).
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_dfs(HV* stash, U32 level)Takes the necessary steps (cache invalidations, mostly) when the @ISA of the given package has changed. Invoked by the setisa magic, should not need to invoke directly.
void mro_isa_changed_in(HV* stash)Call this function to signal to a stash that it has been assigned to another spot in the stash hierarchy. stash is the stash that has been assigned. oldstash is the stash it replaces, if any. gv is the glob that is actually being assigned to.
This can also be called with a null first argument to indicate that oldstash has been deleted.
This function invalidates isa caches on the old stash, on all subpackages nested inside it, and on the subclasses of all those, including non-existent packages that have corresponding entries in stash.
It also sets the effective names (HvENAME) on all the stashes as appropriate.
If the gv is present and is not in the symbol table, then this function simply returns. This checked will be skipped if flags & 1.
void mro_package_moved(HV * const stash, HV * const oldstash, const GV * const gv, U32 flags)CV's can have CvPADLIST(cv) set to point to an AV.
For these purposes "forms" are a kind-of CV, eval""s are too (except they're not callable at will and are always thrown away after the eval"" is done executing). Require'd files are simply evals without any outer lexical scope.
XSUBs don't have CvPADLIST set - dXSTARG fetches values from PL_curpad, but that is really the callers pad (a slot of which is allocated by every entersub).
The CvPADLIST AV has does not have AvREAL set, so REFCNT of component items is managed "manual" (mostly in pad.c) rather than normal av.c rules. 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.
During compilation: PL_comppad_name is set to the names AV. PL_comppad is set to the frame AV for the frame CvDEPTH == 1. PL_curpad is set to the body of the frame AV (i.e. AvARRAY(PL_comppad)).
During execution, PL_comppad and PL_curpad refer to the live frame of the currently executing sub.
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();For state vars, SVs_PADSTALE is overloaded to mean 'not yet initialised'
AV * CvPADLIST(CV *cv)Create a new compiling padlist, saving and updating the various global vars at the same time as creating the pad itself. The following flags can be OR'ed together:
padnew_CLONE this pad is for a cloned CV
padnew_SAVE save old globals
padnew_SAVESUB also save extra stuff for start of sub
PADLIST* pad_new(int flags)When Perl is run in debugging mode, with the -d switch, this SV is a boolean which indicates whether subs are being single-stepped. Single-stepping is automatically turned on after every step. This is the C variable which corresponds to Perl's $DB::single variable. See PL_DBsub.
SV * PL_DBsingleWhen Perl is run in debugging mode, with the -d switch, this GV contains the SV which holds the name of the sub being debugged. This is the C variable which corresponds to Perl's $DB::sub variable. See PL_DBsingle.
GV * PL_DBsubTrace variable used when Perl is run in debugging mode, with the -d switch. This is the C variable which corresponds to Perl's $DB::trace variable. See PL_DBsingle.
SV * PL_DBtraceThe C variable which corresponds to Perl's $^W warning variable.
bool PL_dowarnThe GV which was last used for a filehandle input operation. (<FH>)
GV* PL_last_in_gvThe glob containing the output field separator - *, in Perl space.
GV* PL_ofsgvThe input record separator - $/ in Perl space.
SV* PL_rsDeclare Just SP. This is actually identical to dSP, and declares a local copy of perl's stack pointer, available via the SP macro. See SP. (Available for backward source code compatibility with the old (Perl 5.005) thread model.)
djSP;True if this op will be the return value of an lvalue subroutine
Given a chunk of memory, link it to the head of the list of arenas, and split it into a list of free SVs.
void sv_add_arena(char *const ptr, const U32 size, const U32 flags)Decrement the refcnt of each remaining SV, possibly triggering a cleanup. This function may have to be called multiple times to free SVs which are in complex self-referential hierarchies.
I32 sv_clean_all()Attempt to destroy all objects not yet freed
void sv_clean_objs()Deallocate the memory used by all arenas. Note that all the individual SV heads and bodies within the arenas must already have been freed.
void sv_free_arenas()Return an SV with the numeric value of the source SV, doing any necessary reference or overload conversion. You must use the SvNUM(sv) macro to access this function.
NOTE: this function is experimental and may change or be removed without notice.
SV* sv_2num(SV *const sv)Find the name of the undefined variable (if any) that caused the operator o to issue a "Use of uninitialized value" warning. If match is true, only return a name if it's value matches uninit_sv. So roughly speaking, if a unary operator (such as OP_COS) generates a warning, then following the direct child of the op may yield an OP_PADSV or OP_GV that gives the name of the undefined variable. On the other hand, with OP_ADD there are two branches to follow, so we only print the variable name if we get an exact match.
The name is returned as a mortal SV.
Assumes that PL_op is the op that originally triggered the error, and that PL_comppad/PL_curpad points to the currently executing pad.
NOTE: this function is experimental and may change or be removed without notice.
SV* find_uninit_var(const OP *const obase, const SV *const uninit_sv, bool top)Print appropriate "Use of uninitialized variable" warning
void report_uninit(const SV *uninit_sv)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).
The autodocumentation system was originally added to the Perl core by Benjamin Stuhl. Documentation is by whoever was kind enough to document their functions.