I cannot see how to use. XML::LibXML::XPathContext

The man page says:

       registerNs
             $xpc->registerNs($prefix, $namespace_uri)

           Registers namespace $prefix to $namespace_uri.
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But I do not know in advance what the prefix will be.

     <?xml version="1.0" encoding="utf-8" ?>
     <propfind xmlns="DAV:">
       <propname/>
     </propfind>
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Is valid and

     <?xml version="1.0" encoding="utf-8" ?>
     <D:propfind xmlns:D="DAV:">
       <D:prop xmlns:R="http://ns.example.com/boxschema/">
         <R:bigbox/>
         <R:author/>
         <R:DingALing/>
         <R:Random/>
       </D:prop>
     </D:propfind>
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is valid too.

Worik

But I do not know in advance what the prefix will be.

You don't need to know it, a prefix is for your xpaths, the namespace is important not the prefix, the prefix is just a shortcut for the namespace

The person writing xml "registers" a local prefix so they can write their XML with less chars

The person writing xpath "registers" a local prefix so they can write their xpath with less chars

Neither person has to use the same prefix to refer to the same namespace

The prefix used in the XPath doesn't have to match the prefix used in the document. Only the namespaces need to match. Pick a prefix of your liking. See Re^2: xmlns and XML::LibXML.

I cannot see how to use. XML::LibXML::XPathContext

Please read the replies carefully. A working piece of example code was given to you an hour before you posted this.

The key is that the prefixes used in the XPath expression don't have to have anything to do with the prefixes in the XML file. The following works fine on both your example XML inputs.

my $xml = XML::LibXML->load_xml(string => $txt1);
my $xc = XML::LibXML::XPathContext->new($xml);
$xc->registerNs('foo', 'DAV:');
print "prop:\n";
print "$_\n" for $xc->findnodes('/foo:propfind/foo:prop');
print "propname:\n";
print "$_\n" for $xc->findnodes('/foo:propfind/foo:propname');
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