4 == grep {$_<256} /^(\d+)[.](\d+)[.](\d+)[.](\d+)$/

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Note that 0 is a valid value (unlike certain Microsoft programers thought). 10.0.0.1 is a perfectly fine IP address, for example. You can "golf" this by swapping \. for [.] but I think that mostly just makes it harder to read.

Also note that you might want to outlaw leading zeros since some C programs will incorrectly interpret 10.011.012.013 as containing 3 octal values and won't allow 10.08.09.10 since "08" and "09" aren't valid octal numbers.

4 == grep {$_<256&&!/^0\d/} /^(\d+)[.](\d+)[.](\d+)[.](\d+)$/

[download]

In reply to RE: Matching an IP address by tye
in thread Matching an IP address by bort13

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