I've done it as well, but I've been using Perl to parse HTML since 1994 and XML for four years. In those cases, I also have the file creator within spitting distance, "and he was a poor spitter, lacking both distance and control"(*), so I could literally beat any them over the head if I wanted to. If I didn't have a lot of experience I'd never do it, and if the file provider isn't within strangling distance, I go with CPAN modules.

In short, you can do it, but you probably shouldn't do it.

(*) - P.G. Wodehouse, Money in the Bank