When you say re-learn, what do you need to re-learn?
I always forget commands and all of those sort of things. But the auto complete and search in the manual come in very handy to find exactly what you need in seconds, so as long as you originally know how to put code together, you should be fine?
Comparing it to learning a world language, you could say that you can look up any word easily in a dictionary, but you need to learn the grammar to put it all to use, but once you do get used to the grammar you're pretty much ok for life.
I'm guessing you didn't get too used to the grammar in the first place though which is why you're asking this question?
In that case I can only recommend what frozen fire has said.