Functions wanting an additional "("

I've only recently started using computercraft, so I was expecting to run into errors, but I've been unable to find a solution(or similar problem). I was trying to make a simple testing program to clear a 21x21x2 area out, or at least to do 21x2 then turn so it is positioned to be restarted automatically. However, when i tried to put a turnaround function into the program, i recieved a - bios:366: [string "test"]:4: '(' expected - message.

—-

1. turtle.forward()
3. local function left
4. turtle.turnLeft()
5. end
7. local function aboutFace
8. left
9. turtle.forward()
10. left
11. end
13. aboutFace()

—-
Any help is greatly appreciated.

Basically in most languages when create a function you need to add brackets:

function left()
  --#Your Code
end
local function aboutFace()
  --#Your Code
end

And when you call functions you need to do:
left()
aboutFace()

ah, thank you very much!