Okay, brain-trust, pay attention.

The present perfect tense of "drink" is "have drunk." You can't "have drank" beer before, it just doesn't work. (Although I know a lot of you who have drunk beer before. Many times before.) Now, I know you don't want me to think you're a lush by using the word drunk, but I promise you, I won't. On the other hand, if you use "drank" when you're not supposed to, I will think you're an idiot.