Conditionally executes one block of constructs or statements
  depending on the value of a scalar expression in a SELECT CASE
  statement.  Statement format:

    [name :] SELECT CASE (expr)
    [CASE (case-value [,case-value]...) [name]
      block]...
    [CASE DEFAULT [name]
      block]
    END SELECT [name]

    name   Is the name of the CASE construct.

    expr   Is an expression of type integer, logical, or
           character (enclosed in parentheses). Evaluation
           of this expression results in a value called
           the case index.

    case-value  Is one or more compile-time constant expressions
                of type integer, logical, or character (enclosed
                in parentheses).  Each "case-value" must be of the
                same data type as "expr". If the type is character,
                "case-value" and "expr" can be of different lengths.

                Integer and character expressions can be expressed
                as a range of case values, taking one of the following
                forms:

                low:high
                low:
                :high

                Case values must not overlap.

    block  Is a sequence of zero or more statements or
           constructs.

  If a construct name is specified in a SELECT CASE statement, the
  same name must appear in the corresponding END SELECT statement.
  The same construct name can optionally appear in any CASE statement
  in the construct.

  The case expression ("expr") is evaluated first.  The resulting
  case index is compared to the case values to find a matching value
  (there can only be one).  When a match occurs, the block following
  the matching case value is executed and the construct terminates.

  The following rules determine whether a match occurs:

   o  When the case value is a single value (no colon appears), a
      match occurs as follows:

        Data Type              A Match Occurs If:
        ---------              ---------------------------
        Logical                case-index .EQV. case-value
        Integer or character   case-index ==  case-value

   o  When the case value is a range of values (a colon appears), a
      match depends on the range specified, as follows:

        Range       A Match Occurs If:
        -----       -------------------------
        low:        case-index >= low
        :high       case-index <= high
        low:high    low <= case-index <= high

  The following are all valid case values:

     CASE (1, 4, 7, 11:14, 22)      ! Individual values as specified:
                                    !     1, 4, 7, 11, 12, 13, 14, 22
     CASE (:-1)                     ! All values less than zero
     CASE (0)                       ! Only zero
     CASE (1:)                      ! All values above zero

  If no match occurs but a CASE DEFAULT statement is present, the
  block following that statement is executed and the construct
  terminates.

  If no match occurs and no CASE DEFAULT statement is present, no
  block is executed, the construct terminates, and control passes to
  the next executable statement or construct following the END SELECT
  statement.

  The following are examples of CASE constructs:

    INTEGER FUNCTION STATUS_CODE (I)
      INTEGER I
      CHECK_STATUS: SELECT CASE (I)
      CASE (:-1)
        STATUS_CODE = -1
      CASE (0)
        STATUS_CODE = 0
      CASE (1:)
        STATUS_CODE = 1
      END SELECT CHECK_STATUS
    END FUNCTION STATUS_CODE

    SELECT CASE (J)
    CASE (1, 3:7, 9)    ! Values: 1, 3, 4, 5, 6, 7, 9
      CALL SUB_A
    CASE DEFAULT
      CALL SUB_B
    END SELECT

  The following three examples are equivalent:

    1. SELECT CASE (ITEST .EQ. 1)
       CASE (.TRUE.)
         CALL SUB1 ()
       CASE (.FALSE.)
         CALL SUB2 ()
       END SELECT

    2. SELECT CASE (ITEST)
       CASE DEFAULT
         CALL SUB2 ()
       CASE (1)
         CALL SUB1 ()
       END SELECT

    3. IF (ITEST .EQ. 1) THEN
         CALL SUB1 ()
       ELSE
         CALL SUB2 ()
       END IF