CentOS 5 :: Missing Expat Headers In Package For XML Parser

I Recently set up a dedicated server using CentOS as a new Linux wing of my Web services hosting business. To provision online varios Tucows services (names, blogs etc.) I need to use the Perl API provided by Tucows/OpenSRS. The API requires various extra perl modules including XML::Parser - without which the API will not function.

I was able to add with PPM to my Windows servers no problem but it will not install in CentOS.

As best I can tell the cause may be missing headers and libs for the c compile of Expat - required to build XML::Parser so after days of hunting I found your repository holds package expat-devel which claims to hold libs and headers for Expat similar to libexpat1-dev on other dists. I used YUM with success but although 3 libs were installed no headers were installed.

Is there a reason these headers are not included? I have downloaded them manually but am afraid of breaking something. Is there a reason I should not attempt to install with these headers? Is CentOS capable of using the Parser modules?