[Haskell-beginners] "Trinary" version of Either

Is there a Haskell package out there that provides a "trinary" version of Either, i.e., allowing three values instead of two? I can see how that would be very handy. Defining one obviously wouldn't be difficult, but it would be helpful if someone else had already developed Monad bindings and other related stuff. -- frigidcode.com theologia.indicium.us