FOR variable-name = expression TO expression [ STEP expression ]

   Synopsis:
      Initiates a FOR..NEXT loop

   Notes:
      The expressions must be integers.

   Examples:
      ! Print the numbers 1 to 10 in sequence
      FOR a = 1 TO 10
         PRINT a
      NEXT a

      ! Print the even numbers from 2 to 10 in sequence
      FOR a = 2 TO 10 STEP 2
         PRINT a
      NEXT a

      ! Print the numbers 1 to 10 in reverse sequence
      FOR a = 10 to 1 STEP -1
         PRINT a
      NEXT a
