If you enjoy this sort of thing, there's a really good article by Jérôme Quelin which describes how he wrote a program that is valid on four languages: Perl, C, Befunge, and BrainF*ck. Very interesting read on how to trick the different languages into either working with each others syntax or ignoring parts of the program. http://www.if.insa-lyon.fr/eleves/jquelin/quadri.html