package Foo;
sub new{ return bless{},shift }
sub whois{ print __PACKAGE__ }

package Bar;
sub new{ return bless{},shift }
sub whois{ print __PACKAGE__ }

package Boo;
sub new{ return bless{},shift }
sub whois{ print __PACKAGE__ }

package main;

use base qw(Bar Boo Foo);
use strict;
use warnings;

my $m = main->new;
$m->whois;