package RubberDuck;

sub new { bless {}, shift }

sub quack { print "Squeak!\n" }

sub DESTROY { print "RubberDuck goes back in the toybox.\n" }

package Mallard;

sub new { bless {}, shift }

sub quack { print "Quack!\n" }

sub DESTROY { print "Mallard flies away.\n" }

package main;

for my $duck_class (qw( RubberDuck Mallard ))
{
    my $duck = $duck_class->new();
    $duck->quack();
}