I have been recently playing around with Moose. Here's an example that performs the same task but this time with Moose and coercion.

#!/usr/bin/perl



package Instrument;
use Moose;
has name => ( is => 'rw', isa => 'Str' );



package Beatle;
use Moose;
use Moose::Util::TypeConstraints;

subtype 'Instruments' => as 'ArrayRef';
coerce  'Instruments' => from 'ArrayRef' => via {
    [ map Instrument->new( name => $_ ), @$_ ]
}; 

has name        => ( is => 'rw', isa => 'Str' );
has instruments => ( is => 'rw', isa => 'Instruments', coerce => 1 );

sub plays { map $_->name, @{ shift->instruments } }



package main;
use XML::Simple;

my $xml = XMLin( \*DATA, KeyAttr => [] );

for (@{ $xml->{beatle} }) {

    my $beatle = Beatle->new( %$_ );

    print $beatle->name, ":\n";
    print "\t$_\n" for $beatle->plays;
}


__DATA__
<beatles>
    <beatle name="Paul">
        <instruments>Voice</instruments>
        <instruments>Bass</instruments>
        <instruments>Guitar</instruments>
        <instruments>Piano</instruments>
    </beatle>
    <beatle name="John">
        <instruments>Voice</instruments>
        <instruments>Guitar</instruments>
        <instruments>Rhodes</instruments>
    </beatle>
    <beatle name="George">
        <instruments>Voice</instruments>
        <instruments>Guitar</instruments>
        <instruments>Sitar</instruments>
    </beatle>
    <beatle name="Ringo">
        <instruments>Voice</instruments>
        <instruments>Drums</instruments>
        <instruments>Percussion</instruments>
    </beatle>
</beatles>
[download]

Class::MM requires less code, but Moose offers better encapsulation and type constraints. The tricky part about getting this example to work is dealing with coercion. The neat part here is that there is an implicit notion of a container class for the Instruments, but there is no actual class needed to contain "Instruments."

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)