#!/usr/bin/perl -w

use strict;
use XML::Simple;

my $xs = XML::Simple->new(
  forcearray => [ 'item' ], 
  keyattr    => { },
  rootname   => 'opt',
);

my $opt = $xs->XMLin(\*DATA);

my $id = @{ $opt->{trans}->{item} } + 1;

push @{ $opt->{trans}->{item} }, { id => $id, status => 'contacted', assignee => 'jill' };

print $xs->XMLout($opt);

__DATA__
<opt>
 <trans>
  <item id="1" status="not contacted" assignee="jack" />
 </trans>
</opt>