#!/usr/bin/perl
use warnings;
use strict;

{   package MyCollection;
    use MooseX::Role::Parameterized;

    parameter name => (
        isa => 'Str',
        required => 1,
    );

    parameter member_type => (
        isa => 'Str',
        required => 1,
    );

    role {
        my $p = shift;
        has $p->name => (is => 'ro', isa => 'ArrayRef[' . $p->member_type . ']');
    };

};

{   package MyClass;
    use Moose;
    with MyCollection => { name => 'list', member_type => 'Int' };
    __PACKAGE__->meta->make_immutable;
}

my $obj     = 'MyClass'->new(list => [ 1, 2, 3 ]);
my $invalid = 'MyClass'->new(list => [ 1, 2, 3.14 ]); # Throws as 3.14 is not an Int.