in reply to Parsing EBNF with Perl 5 to eventually parse XML with Perl 6
The only thing to watch out for is that XML can't be parsed using the grammar alone. The comments in the text of the spec are normative, not the grammar. If that wasn't the case I would have used one of the grammar generators (like Parse::YAPP, which can produce a standalone grammar) for XML::SAX::PurePerl.
Still, good effort. If perl 6 ever gets these regexps actually implemented (I have my doubts about that) then it's certainly going to be interesting writing parsers.