use strict;
use warnings;
use XML::Twig;

my $twiga=XML::Twig->new();    # create the twig for data1
$twiga->parsefile( 'data1.xml'); # build it

my $twigb=XML::Twig->new();    # create the twig for data2
$twigb->parsefile( 'data2.xml'); # build it

foreach my $t ($twiga->get_xpath('//host[@id]')) {
	my $att = $t->{'att'}->{'id'};
	unless ($twigb->get_xpath("//host[\@id='$att']")) {
		print "$att is not found in data2.xml\n";
	}
	foreach my $alias ($t->findnodes("host-alias")) {
		my $web = $alias->text;
		unless ($twigb->get_xpath("//host[\@id='$att']/host-alias[string()='$web']")) {
			print "$att with $web is not found in data2.xml\n"
		}
	}
}