Misplaced arguments?

[Leapin]

So I'm working on my first Lua script and I thought I'd make a simple addon without any XML and without the need of extra frames and stuff, either way, what I am trying to do is whenever someone joins the guild, it will announce in gchat "Welcome name", however, for some reason, the "msg" argument seem to be gone from the function. The event says the args are message, sender, language, channel, target etc etc, but when I try to call the first argument, instead of message, it's sender.

local gAuto = CreateFrame("Frame")

gAuto:RegisterEvent("CHAT_MSG_GUILD")
gAuto:SetScript("OnEvent", function(self, event, ...)
 self[event](...)
end)

	function gAuto:CHAT_MSG_GUILD(msg, sender, ...) -- msg = senderName instead of message, and sender = language instead of sender name?
		local str = "has joined the guild"
		name = string.gsub(sender, "-TarrenMill", "")
		name = string.gsub(sender, "-Dentarg", "")
		local welcome = "Välkommen "..name.." :)"
		
		--[[
		if string.find(msg, str) then
				SendChatMessage(welcome, "GUILD")
		else
			return
		end
		--]]
	end

I am really lost, I have no idea what I am doing wrong, any help is appreciated