@clean = ();
@check = ();

open(LIST, 'file.txt') or die "Error 1";

while(<LIST>) {

  chomp $_;

  $count = 0;

  foreach $i (@check) {
    chomp $i;
    if($_ eq $i) { $count++; }
  }

  if($count >= 1) { next; }
  else { push(@clean,$_); push(@check,$_); }
}

close(LIST);