#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;
use XML::Simple qw(:strict);

my $file = <DATA>;
my $ref = XMLin($file,
    KeyAttr    => {item => 'firstname'},
    ForceArray => [ 'item' ],
    ContentKey => '-content'
);  
   
print Dumper($ref);

__DATA__
<opt> 
  <person key="jsmith" firstname="Joe" lastname="Smith" /> 
  <person key="tsmith" firstname="Tom" lastname="Smith" /> 
  <person key="jbloggs" firstname="Joe" lastname="Bloggs" /> 
</opt>