How to put a regex patern in there

I tried many diffirents ways to type the regex patern but bubble never keep it. Does someone can tell me how to do it ?

Hi there, @alain.caron… it looks like you are typing in the search box that appears when you want to insert dynamic data into an expression. If you click away from the input and then click directly in the input and start typing, you shouldn’t see the white box around what you are typing, and whatever you type should be kept in the input.

Hope this helps.