import Data.Maybe

ls :: [String] -> String -> [String]
ls fs p =  map g $ mapMaybe (f p) fs
 where f []     qs   = Just qs
       f (p:ps) (q:qs) 
         | p == q    = f ps qs
         | otherwise = Nothing
       g p = case break ('/'==) p of
               (p',"" ) -> p'
               (p',_:_) -> p'++['/']