Twin naming golf

I saw Brad Fitzpatrick's post on anagram twin names and decided to join in the golf. Weeee!

import Control.Arrow ( first , second , (&&&) , (***) )
import List ( sortBy , groupBy , intersperse )

main = interact $ unlines
       . map ( uncurry (++) )
       . map ( ( ++ " : " ) . fst . head &&& concat . intersperse ", " . map snd )
       . filter ( (> 1) . length )
       . groupBy ( curry $ uncurry (==) . (***) fst fst )
       . sortBy (curry $ uncurry compare . (***) fst fst )
       . map ( sortBy compare &&& id )
       . filter ( not . null )
       . map ( fst . break (== ' ') )
       . lines

hehehe