List.\\ and List.(\\) . The former is in scope, but the latter is not.
The first is a qualified operator, the second is not. The correct syntax to make a qualified operator prefix is (List.\\). There has been some discussion of changing it in Haskell Prime to match your intuition for how it should look, but the change was rejected for H'2010. Maybe it will be adopted in H'2011 or H'2012.
My expectation is that neither of them should be in scope unless we load the List module with with the :m command.
Yes, ghci is decidedly strange in this respect. Any name from any exposed package is available in qualified form at the command prompt, without having to load the module containing it. Indeed, frustratingly, ghci will often complain if you *do* try to load the module: Prelude> :l List <no location info>: module `List' is a package module Failed, modules loaded: none. Regards, Malcolm