If i have a variable ( %requester) when someone type !request #chan, i want that his/her name will be added to %requester and when someone else type !request #chan i want that his/her also will be added then you get this:
%requester nickname1 nickname2
What is the script for that?

Just do a simple: /set %requester %requester nickname_to_add

Would be worth mentioning that he cant have much more than 900 characters in the list of names.

Also might be better to use $addtok to remove same nick being entered twice, although he didnt actually ask for that not to happen.

/set %requester $addtok(%requester,nickname_to_add,32)