I don't know if it's been said anywhere in this thread, but I successfully built expat, and therefore XML::Parser, and HTML::Parser, and the Apache is mod_perl enabled, but you have to edit the config file to enable it. It's a slightly older mod_perl, but all the core Apache::* modules are installed already too (which is what tipped me off to looking for the modperl.so file).

-- Randal L. Schwartz, Perl hacker