[ lookandsay ]          is encode ( $ --> $ )

  [ $ "" 0 rot
    witheach
      [ dup
        char 0 char 9 1+
        within iff
          [ char 0 -
            swap 10 * + ]
        else
          [ swap of join
            0 ] ]
    drop ]                is decode ( $ --> $ )

  $ "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW"
   dup echo$ cr
   encode
   dup echo$ cr
   decode
   echo$ cr