rx of (any SET...)

[Michael Albinus]

Hi,

I have the regexp

--8<---------------cut here---------------start------------->8---
(concat "[^" (bound-and-true-p mm-7bit-chars) "]")
--8<---------------cut here---------------end--------------->8---

I want to write it in rx notation, but I fail. I know how to use xr for
reverse engineering, but I'd like to keep the variable mm-7bit-chars in
the rx notation, and not to replace it by the literal string.

How would this look like?

Best regards, Michael.