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Devel::Refcount(3)    User Contributed Perl Documentation   Devel::Refcount(3)

NAME
       "Devel::Refcount" - obtain the REFCNT value of a referent

SYNOPSIS
	use Devel::Refcount qw( refcount );

	my $anon = [];

	print "Anon ARRAY $anon has " . refcount($anon) . " reference\n";

	my $otherref = $anon;

	print "Anon ARRAY $anon now has " . refcount($anon) . " references\n";

DESCRIPTION
       This module provides a single function which obtains the reference
       count of the object being pointed to by the passed reference value.

FUNCTIONS
   $count = refcount($ref)
       Returns the reference count of the object being pointed to by $ref.

COMPARISON WITH SvREFCNT
       This function differs from "Devel::Peek::SvREFCNT" in that SvREFCNT()
       gives the reference count of the SV object itself that it is passed,
       whereas refcount() gives the count of the object being pointed to. This
       allows it to give the count of any referent (i.e. ARRAY, HASH, CODE,
       GLOB and Regexp types) as well.

       Consider the following example program:

	use Devel::Peek qw( SvREFCNT );
	use Devel::Refcount qw( refcount );

	sub printcount
	{
	   my $name = shift;

	   printf "%30s has SvREFCNT=%d, refcount=%d\n",
	      $name, SvREFCNT($_[0]), refcount($_[0]);
	}

	my $var = [];

	printcount 'Initially, $var', $var;

	my $othervar = $var;

	printcount 'Before CODE ref, $var', $var;
	printcount '$othervar', $othervar;

	my $code = sub { undef $var };

	printcount 'After CODE ref, $var', $var;
	printcount '$othervar', $othervar;

       This produces the output

		       Initially, $var has SvREFCNT=1, refcount=1
		 Before CODE ref, $var has SvREFCNT=1, refcount=2
			     $othervar has SvREFCNT=1, refcount=2
		  After CODE ref, $var has SvREFCNT=2, refcount=2
			     $othervar has SvREFCNT=1, refcount=2

       Here, we see that SvREFCNT() counts the number of references to the SV
       object passed in as the scalar value - the $var or $othervar
       respectively, whereas refcount() counts the number of reference values
       that point to the referent object - the anonymous ARRAY in this case.

       Before the CODE reference is constructed, both $var and $othervar have
       SvREFCNT() of 1, as they exist only in the current lexical pad. The
       anonymous ARRAY has a refcount() of 2, because both $var and $othervar
       store a reference to it.

       After the CODE reference is constructed, the $var variable now has an
       SvREFCNT() of 2, because it also appears in the lexical pad for the new
       anonymous CODE block.

SEE ALSO
       ยท   Test::Refcount - assert reference counts on objects

AUTHOR
       Paul Evans <leonerd@leonerd.org.uk>

perl v5.14.1			  2011-06-21		    Devel::Refcount(3)
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