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package Devel::FindRef;

use common::sense;

use XSLoader;
use Scalar::Util;

BEGIN {
   our $VERSION = 1.46;
   XSLoader::load __PACKAGE__, $VERSION;
}

=head1 NAME

Devel::FindRef - where is that reference to my variable hiding?

=head1 SYNOPSIS

  use Devel::FindRef;

  print Devel::FindRef::track \$some_variable;

=head1 DESCRIPTION

Tracking down reference problems (e.g. you expect some object to be
destroyed, but there are still references to it that keep it alive) can be
very hard. Fortunately, perl keeps track of all its values, so tracking
references "backwards" is usually possible.

The C<track> function can help track down some of those references back to
the variables containing them.

For example, for this fragment:

   package Test;

   use Devel::FindRef;
   use Scalar::Util;
                         
   our $var = "hi\n";
   my $global_my = \$var;
   our %global_hash = (ukukey => \$var);
   our $global_hashref = { ukukey2 => \$var };
                           
   sub testsub {
      my $testsub_local = $global_hashref;
      print Devel::FindRef::track \$var;
   }

   my $closure = sub {
      my $closure_var = \$_[0];
      Scalar::Util::weaken (my $weak_ref = \$var);
      testsub;
   };

   $closure->($var);

The output is as follows (or similar to this, in case I forget to update
the manpage after some changes):

   SCALAR(0x7cc888) [refcount 6] is
   +- referenced by REF(0x8abcc8) [refcount 1], which is
   |  the lexical '$closure_var' in CODE(0x8abc50) [refcount 4], which is
   |     +- the closure created at tst:18.
   |     +- referenced by REF(0x7d3c58) [refcount 1], which is
   |     |  the lexical '$closure' in CODE(0x7ae530) [refcount 2], which is
   |     |     +- the containing scope for CODE(0x8ab430) [refcount 3], which is
   |     |     |  the global &Test::testsub.
   |     |     +- the main body of the program.
   |     +- the lexical '&' in CODE(0x7ae530) [refcount 2], which was seen before.
   +- referenced by REF(0x7cc7c8) [refcount 1], which is
   |  the lexical '$global_my' in CODE(0x7ae530) [refcount 2], which was seen before.
   +- the global $Test::var.
   +- referenced by REF(0x7cc558) [refcount 1], which is
   |  the member 'ukukey2' of HASH(0x7ae140) [refcount 2], which is
   |     +- referenced by REF(0x8abad0) [refcount 1], which is
   |     |  the lexical '$testsub_local' in CODE(0x8ab430) [refcount 3], which was seen before.
   |     +- referenced by REF(0x8ab4f0) [refcount 1], which is
   |        the global $Test::global_hashref.
   +- referenced by REF(0x7ae518) [refcount 1], which is
   |  the member 'ukukey' of HASH(0x7d3bb0) [refcount 1], which is
   |     the global %Test::global_hash.
   +- referenced by REF(0x7ae2f0) [refcount 1], which is
      a temporary on the stack.

It is a bit convoluted to read, but basically it says that the value