rightmost stage, where the head `4` is supplied to `f2`, as the `abort_handler` to
use if that stage decides it has an early answer.
-Finally, notice that we don't have the result of applying `f2` to `4` etc given as
-an argument to the application of `f2` to `5` etc. Instead, we pass
+Finally, notice that we're not supplying the application of `f2` to `4` etc as an argument to the application of `f2` to `5` etc---at least, not directly. Instead, we pass
- (\result_of_foldiing_over_4321. f2 5 result_of_folding_over_4321 <one_handler> <another_handler>)
+ (\result_of_folding_over_4321. f2 5 result_of_folding_over_4321 <one_handler> <another_handler>)
*to* the application of `f2` to `4` as its "continue" handler. The application of `f2`
to `4` can decide whether this handler, or the other, "abort" handler, should be