Ach... won the first time. Beginner's luck

You have to think backwards. Simply put, you need to ensure that there are 2 pearls left for your last move, and take one.

The move before that ideally you want to leave 4, in a 2 by 2 block. At that point he's screwed.

I haven't worked further back than that, but it wouldn't shock me to discover that the person that goes second can always win.