Transformation from XML to HTML is usually done by XSL(T). There are a bunch of XSLT-processors you can choose from. Last time I needed one (3 years ago) Sablotron was the one most complete for the given task. It has a Perl-interface named XML::Sablotron too.

I'm sure in the meantime there are a lot more of them out there.

-- slayven
        trust in bash
        but tie your camel