perl6 will definitely not backwards compatible. AFAICT, if any extension is used, it will probably still be '.pl'. the hash bang line (at least in unix land) determines the specific interpreter to use. Besides that, perl6 is not quite production ready (although this it is supposed to be christmas this year). Perl6 doesn't even have one specific implementation, although it sounds like the first production ready version will be rakudo on top of the MoarVM.
Perl5 would be a much saner default. I would worry about supporting some version of perl6 at a later time.
Perl5 would be a much saner default. I would worry about supporting some version of perl6 at a later time.
btw, cool tool!