Problem Statement

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If the program uses UTF-8 or UTF-16,   it must work on any valid Unicode code point, whether in the   Basic Multilingual Plane   or above it. The program must reference logical characters (code points),   not 8-bit code units for UTF-8 or 16-bit code units for UTF-16. Programs for other encodings (such as 8-bit ASCII, or EUC-JP) are not required to handle all Unicode characters.

Let's start with the solution:

  [ $ "abcdefgh" ] is s  ( --> $ )
  [ 2 ]            is n  ( --> n )
  [ 3 ]            is m  ( --> n )
  [ char d ]       is ch ( --> c )
  [ $ "cd" ]       is ss ( --> $ )

  s n split nip m split drop echo$ cr
  s n split nip echo$ cr
  s -1 split drop echo$ cr
  ch s tuck find split nip m split drop echo$ cr
  ss s tuck find$ split nip m split drop echo$ cr