NAME

       Internals - Reserved special namespace for internals related functions

SYNOPSIS

           $is_ro= Internals::SvREADONLY($x)
           $refcnt= Internals::SvREFCNT($x)
           hv_clear_placeholders(%hash);

DESCRIPTION

       The Internals namespace is used by the core Perl development team to expose certain low level internals
       routines for testing and other purposes.

       In theory these routines were not and are not intended to be used outside of the perl core, and are
       subject to change and removal at any time.

       In practice people have come to depend on these over the years, despite being historically undocumented,
       so we will provide some level of forward compatibility for some time. Nevertheless you can assume that
       any routine documented here is experimental or deprecated and you should find alternatives to their use.

   FUNCTIONS
       SvREFCNT(THING [, $value])
           Historically  Perl  has  been  a  refcounted  language. This means that each variable tracks how many
           things reference it, and when the variable is no longer referenced it will automatically free itself.
           In theory Perl code should not have to care about this, and in a future version Perl might change  to
           some other strategy, although in practice this is unlikely.

           This  function  allows  one  to violate the abstraction of variables and get or set the refcount of a
           variable, and in generally is really only useful in code that is testing refcount behavior.

           *NOTE* You are strongly discouraged  from  using  this  function  in  non-test  code  and  especially
           discouraged  from  using  the  set  form  of  this  function.   The results of doing so may result in
           segmentation faults or other undefined behavior.

       SvREADONLY(THING, [, $value])
           Set or get whether a variable is readonly or not. Exactly what the readonly flag means depend on  the
           type of the variable affected and the version of perl used.

           You  are  strongly discouraged from using this function directly. It is used by various core modules,
           like "Hash::Util", and the "constant" pragma to implement higher-level behavior which should be  used
           instead.

           See  the  core  implementation  for the exact meaning of the readonly flag for each internal variable
           type.

       hv_clear_placeholders(%hash)
           Clear any placeholders from a locked hash. Should not be used directly.  You should use  the  wrapper
           functions    provided    by    Hash::Util    instead.     As    of    5.25    also    available    as
           Hash::Util::_clear_placeholders(%hash)

AUTHOR

       Perl core development team.

SEE ALSO

       perlguts Hash::Util constant universal.c

perl v5.38.2                                       2025-04-08                                   Internals(3perl)