The Xerces c based parser is available as a Perl module. There is the Xerces-Perl home page, and the module can be found on CPAN XML::Xerces.

According to the Xerces-Perl home page the code is only supported on BSD/Linux/Solaris yet, though they plan to port it to Windows eventually.

Because Unicode support is a bit flakey in Perl 5.6.x it's best to have Perl 5.7.x or better for Unicode support, or better still the current 5.8.x version.

You don't say if you have to have Xerces, or if you are just looking at XML in general, but don't forget Perl's many other excellent XML tools (including):

• XML::LibXML and XML::LibXSLT are also c based, and very fast - a particular favourite
• XML::DOM if you need a W3C DOM interface
• XML::GDOME if you need a DOM level 2 iterface
• XML::Parser if you want low level access to your XML
• XML::Sablotron another fast c based parser/XSLT engine
• XML::Simple a classic simple interface to XML in Perl
• XML::TreeBuilder a useful yet underused XML tree manipulation module
• XML::Twig another Perlish XML interface

Mirod has nice articles on Perl/XML - Ways To Rome and What's Wrong with Perl and XML?. Some of the above modules also have reviews in the Module Reviews Section here at PerlMonks.

Update: Updated to reflect recent changes.