Script to parse a text file, extract IPs, and print unique values.

gistfile1.pl

#!/usr/bin/env perl
use strict;
use warnings;

#Array to hold the results.
my %uniqueIPs;
my $index_of;
my $sub;

#Open the file.
open FILE, "file.txt" or die "Couldn't open file: $!\n";
my @fileLines = <FILE>;

#Loop through the lines.
foreach my $line(@fileLines) {
        #Check if the line has an IP in it.
        $index_of = index($line, "10.");

        #See if the number exists!
        if($index_of != -1) {
                #Get a substring with the whole IP.
                $sub = substr($line, $index_of);

                #See if it's in the result array already or not.
                if(!exists($uniqueIPs{$sub})) {
                        #Add the element.
                        $uniqueIPs{$sub} = 1;
                }
        }
}

#Close the file...
close(FILE);

#Write the known keys!
foreach my $IP (keys(%uniqueIPs)) {
        print "$IP";
}