`printout`

      sub printout {
        for my $i (0 .. $#{$chain[1]}){
          my $chars = "";
          for (@chain) { 
            if ($ct_scanout) {
              $_->[$i] =~ tr/01/LH/; 
            } else {
              $_->[$i] =~ tr/X/0/;
            }
            $chars .= $_->[$i];
          }
          print OUTFILE 
            $ct_scanout ? "\n(ct_so\n" : "\n(ct_si  $ct_si{tdi}\n",
            "$chars\n )";
        }
      }

Now an inspiration:
- Why do the trs one character at a time?
- tr can transform $chars all at once!