indeed. cyclic references *can* be a bitch though, especially in situations where one has a lot of inter-operating objects in a persistent Perl interpreter, eg mod_perl. consider: 

#!/usr/bin/perl -w

use strict;

package A;
{
    sub new {
        my $class = shift;
        return bless( { @_ }, $class );
    }

    sub DESTROY {
        warn "$_[0] just died";
    }

    sub set {
        $_[0]->{ $_[1] } = $_[2];
    }
}

package B;
{
    @B::ISA = qw/ A /;
}

package C;
{
    @C::ISA = qw/ A /;
}

package main;

warn "doing something...\n";
do_something();

warn "doing something else (again)...\n";
do_something();

warn "exiting program...\n";

exit;

sub do_something {
    warn "entering block...\n";
    my $a = new A ();
    my $b = new B ();
    my $c = new C ();
    $b->set( C => $c );
    $c->set( B => $b );
    warn "exiting block\n";
}


# output of above:
doing something...
entering block...
exiting block...
A=HASH(0x804b424) just died at ./test_objects.pl line 13.
doing something else (again)...
entering block...
exiting block...
A=HASH(0x805d074) just died at ./test_objects.pl line 13.
exiting program...
C=HASH(0x805bb10) just died at ./test_objects.pl line 13 during global
+ destruction.
B=HASH(0x805b9f0) just died at ./test_objects.pl line 13 during global
+ destruction.
C=HASH(0x805d08c) just died at ./test_objects.pl line 13 during global
+ destruction.
B=HASH(0x804b424) just died at ./test_objects.pl line 13 during global
+ destruction.

[download]

Voila, an unclaimed cyclic reference every time you call do_something(), or any other code that creates object that store references to each other. This is surprisingly easy to do in a large, multi object/reference system, and irritatingly difficult to track down when it happens. meanwhile, your httpd's are growing and growing with every page request....

matt

In reply to Re: Re: Re: Tracing zombie variables. by d_i_r_t_y
in thread Tracing zombie variables. by ash

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