At this point I would not use XML::Parser as the base for a new tool, I would go the XML::LibXML way, unless libxml2 does nor run on the system you plan to use.

If you need W3C schema support note that Andy Wardley just released []. I (and I am not alone in this, see this (long!) thread on xml-dev) don't like W3C schemas though, Relax NG (pronounced relaxing) seems like a much more sane way to go, see this message from James Clarke.