#!/usr/bin/perl 

# Retrieve Set::Scalar from http://www.perl.com/CPAN/modules/by-module/Set
use Set::Object;

# You'll have to create $brontosaurus and $tyrannosaurus yourself.

$dinos = Set::Object->new($brontosaurus, $tyrannosaurus);
$dinos->insert($triceratops, $brontosaurus);
$dinos->remove($tyrannosaurus, $allosaurus);
foreach my $dino ($dinos->members) { $dino->feed(@plants) }