Yes, this Radius server was written in Perl.. there was an article in perl.com about it recently, you can find it here..

We run this under Perl 5.6.1, so it should accept anything that Perl 5.6.1 can handle, I think.. although their sample regex use some notations that I havent used before (ie: I learnt that ^ is a form of negation only after I read the docs)