When using pattern, it currently renders like this (the rightmost part in green):

Since pattern is a regex, i.e. essentially code, it should be rendered in a monospaced font. In the above example, this would also make it much clearer that the pattern allows spaces. (The space before the final - is very thin and easy to miss if just scanning quickly over the pattern to get a grip on the allowed characters. As it is currently rendered, I would feel the urge to copy-paste it to a monospaced editor to make sure.)