use strict;
use warnings;

{
	package Cat;
	use Moo;
	use Types::Standard -types;
	
	has name => (
		is  => 'ro',
		isa => Str,
	);
}

{
	package Litter;
	use Moo;
	use Types::Standard -types;
	
	has cats => (
		is  => 'ro',
		isa => ArrayRef[InstanceOf['Cat']],
	);
}

my $cat1   = Cat->new(name=>'Garfield');
my $cat2   = Cat->new(name=>'Felix');
my $litter = Litter->new(cats => [$cat1, $cat2, 1]);