Visitor List & Landmark Giver Script (boxed)

Put this script into an object near your landing point -
when it detects a visitor within a range you can adjust (default=20m) it sends them a Landmark (which you put in the same object). It also makes a visitor list that you can read by saying "say list" in chat and reset by saying "reset list".
People who are already on the list don't receive the Landmark again.