@ELSEIF val
val. If it is
True, the preprocessor will continue parsing your script. If val is False,
however, @ELSEIF will branch to the next @ELSEIF, @ELSE,
or @ENDIF statement. Note that the condition must be a constant
expression since @ELSEIF operates at preprocessor level, i.e. script variables
are not available at that time.
See IF for details and an example.