Adding command /it or /do.

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Use the PlayerSay hook, and find a list of players nearby using a for loop and the ent/FindInSphere, then send everything after /me or /it to the players.

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Is it chat commands you’re trying to figure out how to make?

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hook.Add( "PlayerSay", "Killurself", function( ply, text, public )
	text = string.sub( text, 1 , 4 ) -- If the first four characters are "!kill", run the code below.
	if ( text == "!kill" ) then
end )

The above is server side only! You can use net messages to run code on client side.