Simple example
SELECT CASE (i)
CASE (3,5,7)
PRINT*,"i is prime"
CASE (10:)
PRINT*,"i is > 10"
CASE DEFAULT
PRINT*, "i is not prime and is < 10"
END SELECT
An IF .. ENDIF construct could have been used but a SELECT CASE is neater and more efficient. Another example,
SELECT CASE (num)
CASE (6,9,99,66)
! IF(num==6.OR. .. .OR.num==66) THEN
PRINT*, "Woof woof"
CASE (10:65,67:98)
! ELSEIF((num >= 10 .AND. num <= 65) .OR. ...
PRINT*, "Bow wow"
CASE DEFAULT
! ELSE
PRINT*, "Meeeoow"
END SELECT
! ENDIF