Have you made sure that RedHat has no prepackaged package for XML::Parser? At least a cursory redhat package xml::parser returns http://packages.sw.be/perl-XML-Parser/ (and likely more trusted repository elsewhere) that contains something that looks very much like the appropriate source RPMs for that package.

I am no system administrator, at least not full time, but I prefer to use the OS package manager to install modules into the vendor provided Perl.