How can you have an "explicit requirement" not to end up like Perl 6? Nobody planned to "end up like Perl 6", it's just something that happens when your new, backwards-incompatible version of the language doesn't catch on.

Also, sounds like Go 2 is going to make backwards-incompatible language changes. How is that different from Python 3, or even Perl 6?

Perl 6 decided from the beginning to break away from Perl 5 and not care about backwards compat. That was their choice. We don't make the same choice.

But Go 2 is also introducing backwards incompatible changes, no?

See the doc I linked above: https://github.com/golang/proposal/blob/master/design/28221-...

Probably not. We can add things and we can opt-in remove things (e.g. user says they want v1.14 of language gets them new language features and removes some language features), but we can't change the semantics of existing programs. That is, if a program compiles with two different language versions, that program should mean the same in both versions.