I'm trying to migrate some code from XML::Twig to XML::LibXML for it's performance advantages. I've been trying with great difficulty to use XML::LibXML to parse dynamically created XML in which the element namespaces are not known prior to parsing. I don't care what the default namespaces are, as long as they don't get in the way.

I'm attempting to use findnodes with the recommended (from perlmonks) XML::LibXML::XPathContext module for dealing with the namespaces. Using registerNs doesn't appear to have any visible effect when printing the XML as a string, so I use $node->setNamespace to accomplish that.

my $parser = XML::LibXML->new();
my $doc = $parser->parse_file($file);
my $t = $doc->getDocumentElement;
foreach my $node ($t->findnodes('TransactionList/Transaction/XML')) {
    my $xml = $node->firstChild;
my $xc = XML::LibXML::XPathContext->new($xml);
    foreach (qw( summary histFile fooScore )) {
        $xc->registerNs($_,"urn:$_");
        $node->setNamespace("urn:$_",$_,0);
    }
my $path = '//fooResponse/info/fooTransaction/transactionDetail/histFi
+le:transactionSummary/summary:PacManScore';
my @nodes = $xc->findnodes($path);
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...but I'm still stuck. It appears that when I encounter an element with a default namespace, findnodes refuses to match it without registering some prefix to the URI. I just want to be able to retrieve the nodes using an XPath like:

//fooResponse/info/fooTransaction/transactionDetail/histFile:transacti
+onSummary/summary:PacManScore
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And if I want to create new elements with arbitrary namespaces, I don't want to have to manage the namespaces at every turn.

//*/info/fooTransaction/transactionDetail/*
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//*/info/fooTransaction/transactionDetail/histFile:transactionSummary/
+*
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Please help! :)

<Extract>
  <Service>
    <Name>FooService</Name>
    <Type>Response</Type>
  </Service>
  <TransactionList>
    <Transaction>
      <Tran_Id>90dc-2f633156cbf6</Tran_Id>
      <XML>
        <fooResponse xmlns="http://some.arbitrary.url/" xmlns:ns="http
+://another.arbitrary.url/" xmlns:xsi="http://www.w3.org/2001/XMLSchem
+a-instance">
          <info xmlns="">
            <servicePreferences>
              <ns:requestingCode xsi:nil="true"/>
            </servicePreferences>
            <fooTransaction xmlns:summary="foo">
              <transactionDetail>
                <histFile:transactionSummary xmlns:histFile="http://ye
+t.another.arbitrary.url/">
                  <summary:PacManScore>95.133</summary:PacManScore>
                  <summary:QBertScore>95.133</summary:QBertScore>
                  <summary:FroggerScore>95.133</summary:FroggerScore>
                </histFile:transactionSummary>
              </transactionDetail>
            </fooTransaction>
          </info>
        </fooResponse>
      </XML>
    </Transaction>
  </TransactionList>
</Extract>
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