[hyperpape]

I agree with all that, and you're right about the syntax being difficult.

My one caveat you can have a little more freedom if you're willing to give up some of the patterns of existing shells, at the cost of unfamiliarity. Of course, you also need to be as expressive as shell so far as possible.

Anyway, "set" isn't a high cost to bear. I don't like it, but that's personal preference, and it clearly helps with the syntax of what you're doing.