diff --git a/antisplice.cabal b/antisplice.cabal
--- a/antisplice.cabal
+++ b/antisplice.cabal
@@ -10,7 +10,7 @@
 -- PVP summary:      +-+------- breaking API changes
 --                   | | +----- non-breaking API additions
 --                   | | | +--- code changes with no API change
-version:             0.11.0.3
+version:             0.11.0.4
 
 -- A short (one-line) description of the package.
 synopsis:            An engine for text-based dungeons.
@@ -48,7 +48,7 @@
 
 library
   -- Modules exported by the library.
-  exposed-modules:     Game.Antisplice.Prototypes, Game.Antisplice.Templates, Game.Antisplice.Lang, Game.Antisplice.Monad, Game.Antisplice.Rooms, Game.Antisplice.Errors, Game.Antisplice.Utils.TST, Game.Antisplice.Utils.AVL, Game.Antisplice.Utils.Run, Game.Antisplice.Utils.BST, Game.Antisplice.Utils.Graph, Game.Antisplice.Utils.Counter, Game.Antisplice.Utils.Fail, Game.Antisplice.Monad.Dungeon, Game.Antisplice.Terminal.Repl, Game.Antisplice.Events, Game.Antisplice.Monad.Vocab, Game.Antisplice.Utils.Atoms, Game.Antisplice.Stats, Game.Antisplice.Utils.None, Game.Antisplice.Utils.Focus, Game.Antisplice.SingleUser, Game.Antisplice, Game.Antisplice.Skills, Game.Antisplice.Stereos, Game.Antisplice.Paths, Game.Antisplice.Action
+  exposed-modules:     Game.Antisplice.Prototypes, Game.Antisplice.Templates, Game.Antisplice.Lang, Game.Antisplice.Monad, Game.Antisplice.Rooms, Game.Antisplice.Errors, Game.Antisplice.Utils.TST, Game.Antisplice.Utils.AVL, Game.Antisplice.Utils.Run, Game.Antisplice.Utils.BST, Game.Antisplice.Utils.Graph, Game.Antisplice.Utils.Counter, Game.Antisplice.Utils.Fail, Game.Antisplice.Monad.Dungeon, Game.Antisplice.Terminal.Repl, Game.Antisplice.Events, Game.Antisplice.Monad.Vocab, Game.Antisplice.Utils.Atoms, Game.Antisplice.Stats, Game.Antisplice.Utils.None, Game.Antisplice.Utils.Focus, Game.Antisplice.SingleUser, Game.Antisplice, Game.Antisplice.Skills, Game.Antisplice.Stereos, Game.Antisplice.Paths, Game.Antisplice.Action, Game.Antisplice.Utils.ListBuilder
   
   -- Modules included in this library but not exported.
   -- other-modules:       
diff --git a/src/Game/Antisplice/Utils/ListBuilder.hs b/src/Game/Antisplice/Utils/ListBuilder.hs
new file mode 100644
--- /dev/null
+++ b/src/Game/Antisplice/Utils/ListBuilder.hs
@@ -0,0 +1,57 @@
+{-# LANGUAGE TypeSynonymInstances, MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances, FlexibleContexts #-}
+
+module Game.Antisplice.Utils.ListBuilder where
+
+import Control.Arrow
+import Control.Monad.Trans.Class
+import Control.Monad.Identity
+
+class Monad l => ListBuilder l i | l -> i where
+  li :: i -> l ()
+  buildList :: l () -> [i]
+
+newtype StrictBuilderT i m a = StrictBuilder { runStrictBuilderT :: [i] -> m (a,[i]) }
+type StrictBuilder i = StrictBuilderT i Identity
+
+instance Functor m => Functor (StrictBuilderT i m) where
+  fmap f a = StrictBuilder $ \s -> fmap (first f) $ runStrictBuilderT a s
+
+instance Monad m => Monad (StrictBuilderT i m) where
+  return a = StrictBuilder $ \s -> return (a,s)
+  m >>= f = StrictBuilder $ \s -> do (a,s') <- runStrictBuilderT m s; runStrictBuilderT (f a) s'
+
+instance MonadTrans (StrictBuilderT i) where
+  lift m = StrictBuilder $ \s -> do a <- m; return (a,s)
+
+instance ListBuilder (StrictBuilder i) i where
+  li a = seq a $ StrictBuilder $ \s -> return ((),s++[a])
+  buildList m = snd $ runIdentity $ runStrictBuilderT m []
+
+strictBuild :: StrictBuilderT i Identity () -> [i]
+strictBuild = buildList
+
+newtype LazyBuilderT i m a = LazyBuilder { runLazyBuilderT :: ([i] -> [i]) -> m (a,[i] -> [i]) }
+type LazyBuilder i = LazyBuilderT i Identity
+
+instance Functor m => Functor (LazyBuilderT i m) where
+  fmap f a = LazyBuilder $ \s -> fmap (first f) $ runLazyBuilderT a s
+
+instance Monad m => Monad (LazyBuilderT i m) where
+  return a = LazyBuilder $ \s -> return (a,s)
+  m >>= f = LazyBuilder $ \s -> do (a,s') <- runLazyBuilderT m s; runLazyBuilderT (f a) s'
+
+instance MonadTrans (LazyBuilderT i) where
+  lift m = LazyBuilder $ \s -> do a <- m; return (a,s)
+
+instance ListBuilder (LazyBuilder i) i where
+  li a = LazyBuilder $ \s -> return ((),s.([a]++))
+  buildList m = ($[]) $ snd $ runIdentity $ runLazyBuilderT m ([]++)
+
+lazyBuild :: LazyBuilderT i Identity () -> [i]
+lazyBuild = buildList
+
+lis :: ListBuilder l i => [i] -> l ()
+lis = mapM_ li
+
+lit :: ListBuilder l (a,b) => a -> b -> l ()
+lit a b = li (a,b)