[thatcks]

As far as I can see, generalized control flow complicates the situation because you need to propagate a variety of signalling results up the tree. Consider a for loop with a switch inside of it, inside of which is an if with a return; if you hit that return, you need to propagate 'return from the function with this result' out through the containing if, switch, and for loop, which means that the Eval() or equivalent for each of them probably all need to know about all of your early-return options (since a 'break' is different from a 'return', especially if you support multi-level breaks).

(I'm the author of the linked-to article.)