LibXML, XPath and Namespaces

space_monk has asked for the wisdom of the Perl Monks concerning the following question:

Dear fellow Monks,

I am in receipt of an xml message. What is the best way to retrieve the xmlns (namespace) attribute from the root element of that message using XML::LibXML?? If it helps, I am expecting GovTalkMessages of the format:

<?xml version="1.0"?>
<GovTalkMessage xmlns="http://www.govtalk.gov.uk/CM/envelope">
<EnvelopeVersion>2.0</EnvelopeVersion>
<Header>
<MessageDetails>
.....
</MessageDetails>
</Header>
<GovTalkDetails>
.....
</GovTalkDetails>
<Body>
<!-- A valid Body payload with a namespace declaration on the first el
+ement -->
</Body>
</GovTalkMessage>
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For bonus points, please tell me if there is any way of avoiding using XPathContext and adding the namespace identifier to all xpath queries on the resulting DOM. e.g. do I really have to do:

   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');
[download]

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