Don't roll your own: 
  use Net::IPv4Addr qw( :all );
  if ($ip = ipv4_checkip($str)) {
      # do something
  }

[download]
This also handles IP+netmask strings like "123.45.67.89/255.255.255.0".

In reply to RE: Check IP addresses for good form by knight
in thread Check IP addresses for good form by Ground Control

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