IMO, that's a very wrong thing to do. It won't teach you *anything*. If code works, or if you think it works just because it happens to produce the right output on a few test cases, it's just luck. It won't give you much insight.

while i generally agree with that, i must say that it sometimes happens to me that i find myself trying out things until i get what i want. of course checking the docs before or after is crucial, but, to tell the truth, i learned a lot of cool perl features by trying out, just for the fun of it. (mostly that happened when playing golf or something, less often when i program production code)
being curious and creative can help becoming a good programmer, IMHO.