Odd, I could have sworn I read all the posts on the way by. If not, then I apologize for posting essentially a duplicate solution. However, mine does in fact work if you run it, so you're wrong on that.
Re^3: help required for regexp
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Oh, hmm. It works the way I intended it, but apparently not the way he did - I went with his pattern of f followed by digits, rather than his intent of just matching the digits. But I can't downvote myself.