There are a lot of different sort of ways to do it, I think, but you may want to try looking into Win32::Registry or Win32::TieRegistry and hitting the right key. Look around on Google (I found the info here), and realize that any registry mucking is dangerous.

Keep in mind, that you may not be able to do it while IE is running (well you could, but it may not take hold). You'll wanna search MSDN to search to see if there is an appropriate OM call. What exactly are you looking to do?