Apache Xerces Perl API
   Includes a collection of Perl5 wrapper objects that internally use their XML4C counterparts for Level 1 DOM processing.
   http://xerces.apache.org/xerces-p/

Performance Comparison Between SAX XML::Filter::Dispatcher and XML::Twig
   XML::Twig and the XML::SAX-based module XML::Filter::Dispatcher offer similar capabilities for implementing XPath-based dispatch tables. A performance comparison shows that they can have nearly identical execution speed.
   http://tomacorp.com/perl/xml/saxvstwig.html

XML::DOM::Twig
   Helper module that adds XML::Twig methods to XML::DOM.
   http://www.xmltwig.com/domtwig/

XML::MetaGenerator
   Collects user input, validates input and generates output in a number of ways based on the defined grammar.
   http://search.cpan.org/~brujah/XML-MetaGenerator/

XML::RSS
   A basic framework for creating and maintaining RSS files.
   http://perl-rss.sourceforge.net/

XML::Twig
   Provides a way to process large XML documents in tree mode.
   http://www.xmltwig.com/xmltwig/

XML::XPath
   XPath parser and evaluator.
   http://xml.sergeant.org/xpath.xml

XML::XSLT
   A Perl module that will convert XML documents on the basis of an XSL template.
   http://xmlxslt.sourceforge.net/