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m/^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\$/;

use strict;
my @nums;
...

# test each for <= 255 here.
# also make sure its not 0.0.0.0

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])$/;