I just wanted to point out something that your response seems to imply.
You do have a word break and then a new line at the end, but there isn't a space before it.
Even if he had a space before the newline it wouldn't match, because there wouldn't be a word break between the space and the end of the string. As inman says below, I can't think of any situation where / \b$/ would match. I'm not sure what it is about the word break anchor, but it seems to be the most misunderstood of the anchors. I know I had problems getting a grasp on it.