It was a good read! Especially since you went through all the details. Handling different inputs and alternates like `after` are a bit tricky. And you're right on the downsides of the "stream" style. There's a bit of overhead compared to the macro form which can inline things a bit. It also takes a couple of more "cognitive" cycles to write, but usually I can read the results more quickly later.

In general I do wish Elixir provided a `reduce` macro similar to the for-loop one with the ability to halt. While-loop logic is easier to refashion as a reduce but it's harder to recall the argument orders for various Enum.reduce forms.

Do you use this while-macro in production code or just test code? Yah the "real" mutability tricks are more for those wondering if you _can_ do it. Sometimes it's not obvious, but one of the nice things in BEAM is that you can cheat.

P.S. thanks for all of your Elixir tools!