I have more or less exactly this syntax written in a notebook as a transformation. The one critique I'd have here is I think that name binding should be handle

I have more or less exactly this syntax written in a notebook as a transformation. The one critique I'd have here is I think that name binding should be handled differently and _not_ introduce extra indentation. Naming shouldn't create indentation IMO, and it's one of the cardinal sources of readability issues in lisps. But for you you could just avoid it entirely (though you might need to be a bit clever about scoping if you care about lifetimes). Just let me write `a = thingy` and then go to my next line!