I could just edit the question and add the correct tag to it. But then a new question could use the same regexp tag in the future, and someone would need to edit that one as well. What is the best practice in this case?
I'd argue that if the tag is a typo it should be edited. But if the tag is a valid name for an existing tag (like regexp for regular-expression in this case). I shall ask for a synonym. Is that correct?
Note 2: When I argue about asking for a synonym, I'm thinking about going to the
:chat! and see if a moderator (or a user with enough reputation) is around.