If you're worried about unique *strings*, you can just try placing each item into a %hash key. When you're all finished, a keys %hash will net you all non-duplicated items. This act of finding unique elements from a list (which this can all be reduced to) is well documented on the site and in various Perl books.

If you're worried about catching duplicate *hostnames* (e.g. "host" v. "host.example.com" could be the same hostname if your domain is example.com), you'll have to try resolving each name individually, and perhaps storing the resulting IP address in the hash instead: 

use Socket;

while (my $item = <FILE>) {
   if (my $ip = gethostbyname($item)) {
      $hash{$ip} = gethostbyaddr($ip, AF_INET) || $item;
   } else {
      # no such hostname
   }
}

print "Unique items:\n";
print "$hash{$_}\n" for keys %hash;

[download]
Note that $ip is in packed form here.

In reply to Re: extract uniques and sort by Fastolfe
in thread extract uniques and sort by ybiC

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