This is the method that $addtok uses, and is described in the help file.
Adds a token to the end of text but only if it's not already in text.
I'm going to presume that you want to keep each person't guesses associated with that person's nick.
You can do this in a number of ways, but the top two I would recommend are using compound variables using the nick as part of the variable name, or using a hash table.
The more people you get, the more I would lean towards the hash table method.
Good luck, and if you want/need more assistance, please be sure to tell us what method you decide to use.
FYI: other methods include using a file (ini or text).