text: -- Zoo2 from notes.org. Path choices requires refining future paths
  
  def Main = {
    a = Match1 ('a'..'z');
    Choose {
      left  = a < 'c' is true;
      right = a >= 'y' is true;
    };
    Choose {
      first  = a < 'e' is true;
      second = a >= 'r' is true; 
    };
  }
  