Since I have never used XML::RSS, I can only offer generic advice.

• A Super Search yields 19 threads related toXML::RSS. Perhaps one of them may give you a clue: ?node_id=3989;HIT=xml%20rss;re=N
• Look at the module's source code (for the version you have installed).
• Post a question on the Discussion forum
• I wouldn't know an RSS if I was kicking one, but have you tried alternate CPAN modules? I wouldn't be suprised if XML::Twig could handle this format.
• Contact the module author by email.