if ($optimize_history) {
    my @history = $term->GetHistory($file);
    my %history;

    # eliminate duplicates in history and keep only the most recent
    for(my $i=scalar(@history)-1;$i>=0;$i--) {
      $_ = $history[$i];
      !$history{$_} ? $history{$_}=1 : splice(@history,$i--,1);
    }

    $term->SetHistory(@history);            # set history to new list
  }
  $term->WriteHistory($file);               # save history