Proper way to halt a script

[Joseph L. Casale]

I am reading perldoc.perl.org and am not understanding exit and die clearly.

If I have a conditional in a sub that I want to validate with, what is the 
correct way to do the following:


1.       End the sub and return back to the script without continuing that sub.

2.       End the entire script without *any* further execution.

How do I write this?

Thanks!
jlc