Back                     Moves Turtle Back

 Back(Distance : Integer);                                            [TG/TP]

    Moves turtle back by the indicated amount. "Back" is relative to the
    turtle's current heading; if the turtle has a heading of 90 (up),
    "back" means in the direction of 180 (down).

        Distance    Distance (in points) to move turtle backwards.

           Note:    A negative value for Distance moves the turtle in the
                    forward direction.

  -------------------------------- Example ---------------------------------

           Back(100);               { move turtle back 100 pixels }