Select Code to Download

<?xml version="1.0"?>
<GovTalkMessage xmlns="http://www.govtalk.gov.uk/CM/envelope">
...
<!-- A valid Body payload with a namespace declaration on the first el
+ement -->
</Body>
</GovTalkMessage>

   my $dom = XML::LibXML->load_xml( string => $xml);
   my $xc = XML::LibXML::XPathContext->new($dom);
   $xc->registerNs( 'gt', 'http://www.govtalk.co.uk/CM/envelope');
   $envelopeVersion = $xc->findvalue( '//gt:EnvelopeVersion');