use warnings;
use strict;

package Foo {
	my $x;
	use overload '<=>'=>sub{1}, 'cmp'=>sub{1}, '0+'=>sub{++$x};
}

my $x = bless {}, 'Foo';
my $y = $x;

print $x==$y ? "True\n" : "False\n";     # False

use Scalar::Util qw/refaddr/;
sub is { return refaddr $_[0] == refaddr $_[1] }

print is($x,$y) ? "True\n" : "False\n";  # True