Keep in mind that a valid IP address is matched by this beast, as found in the Ram Book:

m/^([01]?\d\d|2[0-4]\d|25[0-5])\.([01]?\d\d|2[0-4]\d|25[0-5])\.
   ([01]?\d\d|2[0-4]\d|25[0-5])\.([01]?\d\d|2[0-4]\d|25[0-5])$/;
[download]

Since this is a rather unwieldy expression, and rather static, it should be quite easy to compile it once with qr// and insert it as needed.

-- Dave