study() (correct me if I'm wrong here guys) is only useful if you are going to search many keywords on the same string. Think of it as building an index of where all the a's and the b's, etc.. are located in the string so that if you need to see if 'airplane' is there, you can look really quickly (ok, so it doesn't do exactly that... but it's the same idea! :) ).

So if you are only going to look at a few keywords then don't bother with study, but if you are going to look at a few hundred keywords, then it might help alot more! (The exact cut off value depends on the length of the string, the length of the keywords, and the number of the keywords -- yes the length of the keywords effects the speed of a lookup, both ways).

Cheers,
Gryn