I felt an itch to try to do this in one regex. Admittedly it's a longer string than checking with two short ones, but here's a single regex that I believe does the same thing:

Basically, "There must be a single character that is a letter, a dash, or an underscore. It can also have any number of characters before or after it if none of those characters are anything but word characters (letters or underscores) or dashes."

-BronzeWing