#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

{
    package My::Object;
    use Moose;

    has keys => ( is      => 'ro',
                  traits => ['Array'],
                  handles => { add_keys => 'push',
                               get_keys => 'elements' } );

    __PACKAGE__->meta->make_immutable;
}

my $o = 'My::Object'->new;
$o->add_keys('abc', 'def');

say for $o->get_keys;