I'm going to second this suggestion. I use SAX for most of the XML work I do in Perl because you can use any parsers that are registered without having to worry about which parsers implement what. All you do is pass your requirements for supported features (such as Namespaces) to ParserFactory and it creates an appropriate instance for you.
I would also suggest a look at Perl and XML from O'Reilly. I've found it very useful.
Grant me the wisdom to shut my mouth when I don't know what I'm talking about.