You need to register the namespace, this is made easy with XML::LibXML::XPathContext: 

use XML::LibXML;
use XML::LibXML::XPathContext;
                                                                      
+          
my $xml = q{<?xml version="1.0" encoding="iso-8859-1"?>
<Tag1 xmlns="urn:wow">
  <Foo>content</Foo>
</Tag1>
};
                                                                      
+                                                                     
+                    
                                                                      
+          
my $doc = XML::LibXML->new->parse_string($xml);
my $xc = XML::LibXML::XPathContext->new($doc);
$xc->registerNs('foo', 'urn:wow');
                                                                      
+          
my ($foo) = $xc->findnodes('//foo:Tag1/foo:Foo');
                                                                      
+          
print "Foo in xml: ".$foo->textContent()."\n";

[download]
You can register any arbitrary prefix to your namespace URI to use in your XPath expression but note I have changed your namespace to an absolute URI as you get an error from XML::LibXML otherwise.

/J\

In reply to Re: XML::LibXML findnodes fails when using namespaces by gellyfish
in thread XML::LibXML findnodes fails when using namespaces by jeteve

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