PUG: Side-effect-free parrot
Perl 6 with a haskell/lisp flavor?
Using parrot to enforce coding styles (use strict on steroids) has always seemed like one of the best improvements of perl 6. Hats off to Autrijus for pioneering the technique. I'm not positive this is use-strict style syntactical straightjacket, or whether it's more of a parrot language implementation that shares some perl6 syntax, but it looks like a step in the right direction either way.
Correction: PUGS is in fact a Perl6 interpreter written in Haskell. It doesn't have anything to do with parrot -- the perl 6 vm
Please also see the hilarious imaginary perl6 adoption timeline
Updated: Chris Winters has a timely post on MJD's Higher Order Perl also filled with functional programming goodness. Ugh. My reading list is too long.