Useful alternative control structures?

Question

Sometimes when I am programming, I find that some particular control structure would be very useful to me, but is not directly available in my programming language. I think my

Answer 1

With (lisp-style) macros, tail-calls, and continuations all of this is quaint.

With macros, if the standard control flow constructs are not sufficient for a given application, the programmer can write their own (and so much more). It would only require a simple macro to implement the constructs you gave as an example.

With tail-calls, one can factor out complex control flow patters (such as implementing a state machine) into functions.

Continuations are a powerful control flow primitive (try/catch are a restricted version of them). Combined with tail-calls and macros, complex control flow patterns (backtracking, parsing, etc.) become straight-forward. In addition, they are useful in web programming as with them you can invert the inversion of control; you can have a function that asks the user for some input, do some processing, asks the user for more input, etc.

To paraphrase the Scheme standard, instead of piling more features onto your language, you should seek to remove the limitations that make the other features appear necessary.