Do you know setjmp/longjmp in C? It's like that, except you can longjmp to the same target more than once, because Scheme's equivalent of "stack frames" are on

Do you know setjmp/longjmp in C? It's like that, except you can longjmp to the same target more than once, because Scheme's equivalent of "stack frames" are on the garbage-collected heap instead of "the stack". (The implementation may be fancier, but that's the easiest way to do it.)