use strict;
use warnings;

use Template;
use XML::Simple;

my $data = XMLin( $ARGV[0], ForceArray => 'class' );

$data->{class} = 
[ 
	sort 
	{ 
		$a->{strength}->[0] <=> $b->{strength}->[0] 
	} 
	@{$data->{class}} 
];

#use Data::Dumper;
#print Dumper ( $data );

my $tt = Template->new();

$tt->process( \*DATA,  {data => $data}, $ARGV[1] )
	|| die $tt->error(), "\n";

__DATA__
<?xml version="1.0" encoding="UTF-8"?>

<system>

<header></header>

[% FOR class = data.class %]
<class>
<name>[% class.name.0 %]</name>
<strength>[% class.strength.0 %]</strength>
</class>
[% END %]

<footer></footer>
</system>