Maybe it's not intended, but it certainly fits the specification given by the OP.

95% of the effort of finding a regexp is stating actual definition of what you want. If people spend half the time it takes to write down a Perlmonks question in actually formulating what they want, we'd see far less regexp questions here, and we'd need to do far less guessing of what the OP wants. Because if what is wanted isn't stated accurately, all that can be done is play the lottery, and guess what is wanted.