negative commands: with our without 了?
I have been going through the grammar lessons on resources.allsetlearning.com, and have just run into a question / an unclear point. The following two links talk about the use of 别 with negative commands:
However, the second one says that you use "bie" with "le", whereas the first one says that you simply use "bie". Which one is correct? and if both are correct, what is the difference between them?
Thanks so much,