#!/usr/bin/perl -w
use strict;
use warnings;

my @a = ();
my $foo = bless \@a, 'Cleanup';
print $foo;

package Cleanup;

use overload
  q{""}   => sub { undef },
  #q{""}   => sub { "foo" },
  q{0+}   => sub { undef },
  q{bool} => sub { undef };

1;