[ken]

It is to me. The alternative is implementing them ad-hoc in every function. (Or perhaps waiting another few decades for Swift to add them to its compiler.) Having used many languages at different points on the power spectrum, I remain unconvinced that there's any advantage to omitting abstraction capabilities and forcing programmers to deal with it.

Besides, both of those examples are essentially non-local jumps, and I'm not sure I'd describe them as "modern".

In a sense, Swift already allows diversity in control flow constructs, via closures and the trailing closure syntax. It's just somewhat awkward, and not flexible enough to implement, say, most of Lisp's ITERATE library. That's packed full of exactly the kinds of control flow constructs that I have to write out by hand in Swift every day.