Do you want to loop again or continue the current loop?

 

What are you trying to do because it doesn't make any sense. If you tell us we can tell you a way to accomplish what you're trying to do.
Because it doesn't make any sense to loop all players and then set {_player} to a random element out of players. Because if you are using a command to find a random player or a event you can just set {_player} to a random element out of players whidout the need to loop all players. Why do you want to choose a player and then repeat the loop again?
This is what I think too are trying to do

Code (Text):

1. Function FindPlayer():
2.     Set {_player} to a random element of all players
3.     If {_player} is "player1" or "player2":
4.         #code if you find the player
5.     Else:
6.         Findplayer()#repeat loop again
7.         Wait a tick#or the server will probably crash
8.  
9.  
10. Command /randomplayer:
11.     Trigger:
12.         FindPlayer()

 

You don't need addons and is not necessary to have values inside () but there is a tutorial about function in this page.
But you can try adding this (s: string)
Then when you call the function
FindPlayer("ASDS")