IfNot>expression[,true_label_name[,false_label_name]]
statements
[ [Else
else statements]
Endif ]
The reverse of If. Evaluates expression. If the expression is not true the first statements are executed. If the expression is true the statements after Else are executed. Else is optional. IF blocks can be nested. When label names are provided execution of the script jumps to the specified labels or subroutine names. If label names are specified Else and Endif are ignored and are unnecessary.
For more information on how to use this please see If.