The cynical lesson I've taken from watching languages evolve over time is that, if you wish to provoke mass-migration to your new language version, having eithe

The cynical lesson I've taken from watching languages evolve over time is that, if you wish to provoke mass-migration to your new language version, having either a missing feature people want, or an annoying misfeature people don't, is really important. Java and PHP have had both in spades. Back in the Perl 4 days, people really wanted a real object system[1]. Python 2 (aside from a few things that annoy the crap out of me, but apparently not many others) is a pretty complete, fairly decent language. Perl5 is pretty complete and people are pretty happy with it. (Well, the ones who write in it.) [1] Yes, I know, not here to argue the semantics. It is "sufficiently OO" for what people want to do with it.