I put together a patch for this Haskell' proposal (http://hackage.haskell.org/trac/haskell-prime/ticket/41)
Prelude> (if then "Haskell" else "Cafe") False "Cafe" Prelude> (case of 1 -> "One"; _ -> "Not-one") 1 "One"
There seems to be some support for integrating this proposal into GHC (see http://permalink.gmane.org/gmane.comp.lang.haskell.cafe/81366)
The attached patches implement the feature, test it and document it.
See also the wiki page LambdasVsPatternMatching.