The errata for Perl Cookbook at O'Reilly has a modified ip validation re. It is also in ping for ppt by me.

     m{
        ^  ( \d | [01]?\d\d | 2[0-4]\d | 25[0-5] )
       \.  ( \d | [01]?\d\d | 2[0-4]\d | 25[0-5] )
       \.  ( \d | [01]?\d\d | 2[0-4]\d | 25[0-5] )
       \.  ( \d | [01]?\d\d | 2[0-4]\d | 25[0-5] )
        $                               # from the Perl Cookbook, Reci
+pe 6.23,
    }xo                                 # pages 218-9, as fixed in the
+ 01/00 reprint
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HTH
--
idnopheq
Apply yourself to new problems without preparation, develop confidence in your ability to to meet situations as they arrise.

~ Shunryu Suzuki