[Haskell-cafe] Beginner: IORef constructor?

First of all, sorry if this is a really silly question, but I couldn't figure it out from experimenting in GHCi and from the GHC libraries documentation (or Google). Is there an IORef consturctor? Or is it just internal to the Data.IORef module? I want a "global variable", so I did the following: ------ module VirtualWorld where import Data.IORef theWorld = IORef [] -- This will be writeIORef'ed with a populated list as the user modifies the world. ----- It doesn't work. GHCi says that the IORef constructor is not in scope. I did a ":module Data.IORef" and then "IORef []" and it still gives me the same error. I'm using GHC 6.6 on Windows.