There might be one posted in this board somewhere if you look for it.
otherwise look for where the player joins in the scripts file. Then write some code to save their username and unique id, store the string then send it.(dont forget to make the string) how you send it is up to you. i personally hate the spam some servers have when they are full, showing 357202384 messages on the start of a new map. so i went with a way to send it to the player only, so they can read it easier, and less spam on the server.
of course, i hope in the next week or 2 i can get the patch out, which has a welcome message built in. Then people can use that.