Aside from the question of how suitable the items in @list are for your purposes, the logic in read_line's loop doesn't make sense to me. I think that what you want is:

  foreach my $word (@list) {
    print $word, $/ unless $hash{ lc $word }++;
    $count = $hash{ lc $word };
    if ($count > $maxcount) {
      $maxcount = $count;
      $find = $word;
    }
  }
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