use strict;
use warnings;
no warnings 'uninitialized';

use XML::Rules;

my $parser = XML::Rules->new(
	stripspaces => 7,
	rules => {
		'ip-address-ranges' => 'content array',
		'host-group' => sub {
			my ($tag, $attr, $parents, $parent_data) = @_;
			my $name = join '.', ((map $_->{name}, @{$parent_data}[1..$#$parent_data]), $attr->{name});
			if ($attr->{'ip-address-ranges'} && @{$attr->{'ip-address-ranges'}}) {
				foreach my $ip (@{$attr->{'ip-address-ranges'}}) {
					print "$name\t$ip\n";
				}
			} else {
				print "$name\n";
			}
			return;
		}
});

$parser->parse(\*DATA);


__DATA__
<?xml version="1.0" encoding="UTF-8"?>
<sub-group-tree>
...