patterns----------------
(
  [0, "..e......."],
  [11, "..m......."],
  [22, "..e......."],
  [33, "..r......."],
  [44, "..o......."],
  [55, ".m........"],
  [55, "..i......."],
  [55, "...d......"],
  [55, "....d....."],
  [55, ".....i...."],
  [55, "......e..."],
  [55, ".......s.."],
  [66, "..d......."],


##</code><code>##

      my $underpat = qr/[^@under@tiles]/;
      say "underpat is $underpat";
      my @words = grep {
             length $pat == length $_
          && !/$underpat/
          && /^$pat$/
          && ( ( $old ^ $_ ) !~ /^\0+\]$/ )    # adding just an 's' not allowed

##</code><code>##

underpat is (?^u:[^mh h i m q r t])
underpat is (?^u:[^mh h i m q r t])
underpat is (?^u:[^e m e r o i dh h i m q r t])
underpat is (?^u:[^e m e r o i dh h i m q r t])
underpat is (?^u:[^e m e r o i dh h i m q r t])
underpat is (?^u:[^e m e r o i dh h i m q r t])
underpat is (?^u:[^e m e r o i dh h i m q r t])
underpat is (?^u:[^e m e r o i dh h i m q r t])
underpat is (?^u:[^e m e r o i dh h i m q r t])
underpat is (?^u:[^dh h i m q r t])
underpat is (?^u:[^dh h i m q r t])
underpat is (?^u:[^dh h i m q r t])


##</code><code>##

say "new mask is $newmask";
    substr $heights, $pos, length $highs,
      ( $highs & $newmask ) =~ tr/0-4/1-5/r | ( $highs & ~$newmask );