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

my %seen;
open(my $fh, '<', '2of12inf.txt') or die "Unable to open '2of12inf.txt' for reading: $!\n";
while (<$fh>) {
    chomp;
    $_ = lc($_);
    tr/a-z//cd;
    next if ! $_ || length($_) > 8 || $seen{$_}++;
    print "$_\n";
}