continuations

In this thread, you may post code that makes use of continuations, and I will attempt to produce code that does the same and looks reasonably similar, without using continuations.

>>66
Like almost everyone else on this board four years ago, I am trying to achieve computational enlightenment. I wish to see the true essence of computation, and I wonder whether it is purely functional, how powerful macros are, what kind of continuations there are, and so on. So far I am certain that evaluation must be strict, and that it must look and behave mostly like Lisp.

So more to the point, I am wondering whether continuations can be elegantly expressed in terms of some non-deterministic operations which would then generalize them.