[lloeki]

This mimics Perl's "use 5.x", although the latter is scoped per module. Perl's backward compatibility track record validates the soundness of this approach.

Perl can also selectively enable features, in a way not dissimilar to Python's "from _future_ import X", except the latter is about forward compatibility with a future default, whereas Perl is all about backwards compatibility as a sane default.

I guess Go does it at the mod consistent level because it needs a global view of features whereas Perl can dynamically alter itself (including its parser) live.