About Exiting a Function Quietly (AutoLISP)

 
 
 

If you invoke the princ function without passing an expression to it, it displays nothing and has no value to return.

So if you add a call to princ without any arguments, after an expression, there is no return value. This is a great way to suppress the nil that is often returned by the last expression within a custom function. This practice is called exiting quietly.