#!/usr/local/bin/perl
use strict;
use warnings;
use Data::Decycle;
{
    package Dummy;
    sub new { bless $_[1], $_[0] }
    sub DESTROY { warn "($_[0])" }
}

{
    my $guard = Data::Decycle->new();
    add $guard my $mom = Dummy->new( {} );
    add $guard my $son = Dummy->new( {} );
    $mom->{son} = $son;
    $son->{mom} = $mom;
}
warn "Goodbye, world!";