IF ... ELSEIF ... ELSE ... END IF


    IF expr THEN
        { statement }
    { ELSEIF expr THEN
        { statement } }
    [ ELSE
        { statement } ]
    END IF
IF performs conditional operations. For example:

    IF 10 > 12 THEN
        PRINT "10 is less than 12"
    END IF
These tests can be chained together with additional ELSEIF tests, which are performed if the prior tests fail. An optional ELSE clause is executed if none of the prior tests were true:

    IF a = 1 THEN
        PRINT "One"
    ELSEIF a = 1 THEN
        PRINT "Two"
    ELSEIF a = 3 THEN
        PRINT "Three"
    ELSE
        PRINT "Too big!"
    END IF