See CPAN for uncounted number of XML related modules.

The perl-xml mailing list
http://aspn.activestate.com/ASPN/Mail/Browse/Threaded/perl-xml

http://xmltwig.com/

http://perl-xml.sourceforge.net/

http://www.xml.com

"Perl and XML" (first ed) By Erik T. Ray, Jason McIntosh, Published by O'Reilly

Many of our examples are taken from these places either directly or 
after some transformation.