IF lexpr THEN statement_block [ ELSIF lexpr2 THEN statement_block ] [ ELSE statement_block ] END IF
This creates a test, or series of tests. The statement_block under the first lexpr that evaluates to 1 will be executed. Any number of ELSIF clauses are allowed. If no lexpr evaluates to true and the ELSE clause exists, the statement_block for the ELSE clause will be executed.
A special case of the IF statement is when any lexpr is a constant 0. In this case, the statement block is not parsed. This can be used for block comments.
IF 0 this is a dummy block that won't even be parsed! END IF
IF x == 5 THEN y = 7 ELSIF x == 6 THEN y = 12 ELSE y = 0 END IF