Currently, I am doing some tests:
^(:**:)?boss$ ^az$ 0
seems to work: user az is not allowed to have any access to pages in any namespace, which name is "boss", but currently I also do not know exactly why this works. I took some help from chatGPT, etc.
How can I extend it in a way that all pages are touched with end with "boss", f.e., also "2789_boss" should be considered.
@Chris75: I do not understand your post. Most probably due to my negligible knowledge of regex ;-)
Thank you all so far. It all goes into the right direction.