All of the XML processing modules on CPAN are based on
expat, including XML::Parser, XML::PYX, XML::Simple,
XML::Twig and many more.
I fail to see why it is such a problem. Yes it means
you cannot install directly using CPAN. But it installs
very easily under Unix and once again XML::Parser
comes with Activestate's Windows port. I know CPAN
is extremelly convenient but it is not the only valid
method to install modules.
If you want to do any serious XML processing you really
need a proper parser. Using regexps is false laziness.
It is akin to not using strict: good for a
quick hack but a no-no for anything serious.
Incidentally there are good reasons why expat is not
bundled with XML::Parser anymore. It is used by other
applications, Apache for example and bundling it lead
to incompatibilities between the different versions and
problems building them.