How do I check if the selected text includes a new line/return?

I am using an if-condition to check whether the selected text is or includes a linebreak (or return) but I'm not sure how to enter this:


(Nevermind whether the operator is "is" or "contains", what I'm asking about is the field highlighted in blue.)

(Background: I'm trying to check whether the cursor is at the beginning of a line, so if there is another way of doing that, let me know.)