Yes it does:

>All it needs is a little new syntax

You seem to be under the impression that adding new syntax necessarily breaks existing code. But that just isn't true. If you can't fathom how it's done, then look at the use VERSION statement in Perl.

It doesn't just break existing code, it breaks existing tooling for checking syntax ..

(Perl is hardly a decent model.)

This answer that is both so stupendously confident and wrong is only possible if you in actuality decided to not read and understand how this problem is solved in Perl.