Hi there:

Of course I am biased, but how about... (untested)

use strict;
use warnings;

use vars qw($is_this_an_IP_address); 
use NetAddr::IP;

my $ip = new NetAddr::IP $is_this_an_IP_address;

if ($ip)
{
  # This is a valid IP address, or something an IP address can be deri
+ved
  # from
}
else
{
  # This is not an IP address
}
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