Syntax:  SET LANGUAGE IDENTIFIER CHARACTERS identifier_characters
              defined_language

  Specifies the characters that may appear in token and alias names in
  the language.

  The list of identifier characters also determines what LSE considers
  to be a word.  A word is a sequence of identifier characters,
  possibly followed by one or more blanks, tabs, or nonidentifier
  characters.  All nonblank, nonidentifier characters are considered to
  be distinct words.