Section 13,21: ELSE_IF

 Executes a block of statements if no preceding statement block in a
 block IF construct was executed and if the value of a logical
 expression is true.  The block of statements starts immediately
 following the ELSE IF statement.  The block is terminated by
 another ELSE IF statement, an ELSE statement, or an END IF
 statement.  Statement format:

    ELSE IF (e) THEN

    Where e represents a logical expression.