use strict;
use warnings;

use XML::XPath;
use XML::XPath::XMLParser;

my $xp = XML::XPath->new(filename => 'invoice.xml');

my $nodeset = $xp->find('//Invoice/InvoiceDetails/BaseItemDetails');

foreach my $node ($nodeset->get_nodelist) {
    my $description = $node->find('Description')->string_value;
    print " DES: $description\n";
}