Amber Heartsong

If I have two prims rezzed, I know that I can have a script on prim A that will copy its inventory to prim B using llGiveInventoryList. Is there any functionality that I can have on the script on prim A to view the inventory of prim B, so that I don't send duplicates over? I am attempting to duplicate the functionality of a script based on its description, which includes that it doesn't load duplicated objects onto the recipient prim, but I can't see a way to do that without there being a listener on the recipient prim that gets the object name and type and responds whether or not there is a matching object present.