You are seriously limiting yourself by ruling any CPAN modules out. There are several different XML parsers, including SAX-based parse engines. There is nothing in the Perl core that provides XML parsing, so any solution you adopt will be either something you yourself write, or something installed from elsewhere.

If the concern is over external dependancies (such as expat), there are a few pure-Perl parse solutions, one of which comes from matts's XML::SAX package.

--rjray