One of the easiest ways to transform XML into data structures is XML::Simple. (Though limited, I found it to be sufficient for most uses.) Transforming XSL into TT2 templates seems to be harder but possible with some diligency and motivation.

Oh, Lazy Web, any conversor of XSL into TT2 templates out there? Wondering: how it would be named? XSL::Template, Template::Compiler::XSL, Template::Nice::XML, ...