diff --git a/Setup.hs b/Setup.hs
--- a/Setup.hs
+++ b/Setup.hs
@@ -1,3 +1,3 @@
 #!/usr/bin/env runhaskell
 import Distribution.Simple
-main = defaultMainWithHooks defaultUserHooks
+main = defaultMain
diff --git a/lambdabot-haskell-plugins.cabal b/lambdabot-haskell-plugins.cabal
--- a/lambdabot-haskell-plugins.cabal
+++ b/lambdabot-haskell-plugins.cabal
@@ -1,5 +1,5 @@
 name:                   lambdabot-haskell-plugins
-version:                5.2
+version:                5.3
 
 license:                GPL
 license-file:           LICENSE
@@ -45,8 +45,8 @@
 homepage:               https://wiki.haskell.org/Lambdabot
 
 build-type:             Simple
-cabal-version:          >= 1.8
-tested-with:            GHC == 7.10.3, GHC == 8.0.2, GHC == 8.2.2, GHC == 8.4.4, GHC == 8.6.5
+cabal-version:          >= 1.10
+tested-with:            GHC == 8.2.2, GHC == 8.4.4, GHC == 8.6.5, GHC == 8.8.3
 
 extra-source-files:     src/Lambdabot/Plugin/Haskell/Free/Test.hs
 
@@ -58,6 +58,7 @@
   hs-source-dirs:       src
   ghc-options:          -Wall
                         -funbox-strict-fields
+  default-language:     Haskell98
 
   exposed-modules:      Lambdabot.Plugin.Haskell
 
@@ -98,9 +99,9 @@
                         containers              >= 0.4,
                         directory               >= 1.1,
                         filepath                >= 1.3,
-                        haskell-src-exts-simple >= 1.18.0.0 && < 1.22,
-                        lambdabot-core          >= 5.2 && < 5.3,
-                        lambdabot-reference-plugins >= 5.2 && < 5.3,
+                        haskell-src-exts-simple >= 1.18 && < 1.24,
+                        lambdabot-core          >= 5.3 && < 5.4,
+                        lambdabot-reference-plugins >= 5.3 && < 5.4,
                         lifted-base             >= 0.2,
                         mtl                     >= 2,
                         oeis                    >= 0.3.1,
@@ -119,7 +120,7 @@
                         data-memocombinators    >= 0.4,
                         hoogle                  >= 5.0.17.1,
                         IOSpec                  >= 0.2,
-                        lambdabot-trusted       >= 5.2 && < 5.3,
+                        lambdabot-trusted       >= 5.3 && < 5.4,
                         logict                  >= 0.5,
                         MonadRandom             >= 0.1,
                         mueval                  >= 0.9.3,
diff --git a/src/Lambdabot/Plugin/Haskell/Check.hs b/src/Lambdabot/Plugin/Haskell/Check.hs
--- a/src/Lambdabot/Plugin/Haskell/Check.hs
+++ b/src/Lambdabot/Plugin/Haskell/Check.hs
@@ -7,6 +7,7 @@
 import Lambdabot.Plugin
 import Lambdabot.Plugin.Haskell.Eval (runGHC)
 import qualified Language.Haskell.Exts.Simple as Hs
+import Codec.Binary.UTF8.String
 
 checkPlugin :: Module ()
 checkPlugin = newModule
@@ -22,7 +23,7 @@
 
 check :: MonadLB m => String -> m String
 check src =
-    case Hs.parseExp src of
+    case Hs.parseExp (decodeString src) of
         Hs.ParseFailed l e  -> return (Hs.prettyPrint l ++ ':' : e)
         Hs.ParseOk{}        -> postProcess `fmap` runGHC ("text (myquickcheck (" ++ src ++ "))")
 
diff --git a/src/Lambdabot/Plugin/Haskell/Eval.hs b/src/Lambdabot/Plugin/Haskell/Eval.hs
--- a/src/Lambdabot/Plugin/Haskell/Eval.hs
+++ b/src/Lambdabot/Plugin/Haskell/Eval.hs
@@ -21,8 +21,6 @@
 import System.Exit
 import System.Process
 import Codec.Binary.UTF8.String
-import Network.Browser (request)
-import Network.HTTP (getRequest, rspBody)
 
 evalPlugin :: Module ()
 evalPlugin = newModule
@@ -36,10 +34,6 @@
             , help = say "let <x> = <e>. Add a binding"
             , process = lim80 . define
             }
-        , (command "letlpaste")
-            { help = say "letlpaste <paste_id>. Import the contents of an lpaste."
-            , process = lim80 . defineFromLPaste
-            }
         , (command "undefine")
             { help = say "undefine. Reset evaluator local bindings"
             , process = \s ->
@@ -180,31 +174,6 @@
 munge, mungeEnc :: String -> String
 munge = expandTab 8 . strip (=='\n')
 mungeEnc = encodeString . munge
-
-------------------------------
--- define from lpaste
-
-defineFromLPaste :: MonadLB m => String -> m String
-defineFromLPaste num = do
-  maxlen <- getConfig maxPasteLength
-  mcode <- fetchLPaste num
-  case mcode of
-    Left err   -> return err
-    Right code
-     | length code < maxlen -> define code
-     | otherwise            -> return $
-       "That paste is too long! (maximum length: " ++ show maxlen ++ ")"
-
-fetchLPaste :: MonadLB m => String -> m (Either String String)
-fetchLPaste num = browseLB $
-  if any (`notElem` ['0'..'9']) num
-    then return $ Left "Invalid paste ID."
-    else do
-      let src = "http://lpaste.net/raw/" ++ num
-      (uri, resp) <- request $ getRequest src
-      return $ if show uri == src
-        then Right $ rspBody resp
-        else Left "I couldn't find any paste under that ID."
 
 ------------------------------
 -- reset all bindings
diff --git a/src/Lambdabot/Plugin/Haskell/Free/FreeTheorem.hs b/src/Lambdabot/Plugin/Haskell/Free/FreeTheorem.hs
--- a/src/Lambdabot/Plugin/Haskell/Free/FreeTheorem.hs
+++ b/src/Lambdabot/Plugin/Haskell/Free/FreeTheorem.hs
@@ -9,6 +9,7 @@
 import Lambdabot.Plugin.Haskell.Free.Util
 
 import Control.Monad
+import Control.Monad.Fail (MonadFail)
 import Control.Monad.State
 import Control.Monad.Identity
 
@@ -48,7 +49,7 @@
     = let ts12 = map (extractTypes env) ts
       in (TyCons c (map fst ts12), TyCons c (map snd ts12))
 
-freeTheoremStr :: (Monad m) => (String -> m String) -> String -> m String
+freeTheoremStr :: (MonadFail m) => (String -> m String) -> String -> m String
 freeTheoremStr tf s
     = case parse (do
                     v <- getToken >>= \v -> case v of
@@ -292,6 +293,6 @@
         return (foldr (\((f,t),e1) e2 -> ThForall f t (ThImplies e1 e2))
                 thf fts)
 
-freeTheorem' env e1 e2 t'@_ = fail "Sorry, this type is too difficult for me."
+freeTheorem' env e1 e2 t'@_ = error "Sorry, this type is too difficult for me."
 
 -- vim: ts=4:sts=4:expandtab:ai
diff --git a/src/Lambdabot/Plugin/Haskell/Free/Parse.hs b/src/Lambdabot/Plugin/Haskell/Free/Parse.hs
--- a/src/Lambdabot/Plugin/Haskell/Free/Parse.hs
+++ b/src/Lambdabot/Plugin/Haskell/Free/Parse.hs
@@ -4,6 +4,8 @@
 
 import Control.Applicative
 import Control.Monad
+import Control.Monad.Fail (MonadFail)
+import qualified Control.Monad.Fail
 
 data Token
     = QVarId String
@@ -75,6 +77,8 @@
     m >>= k = ParseS (\ts -> case parse m ts of
                                 ParseSuccess x ts' -> parse (k x) ts'
                                 ParseError s       -> ParseError s)
+
+instance MonadFail ParseS where
     fail str = ParseS (\_ -> ParseError str)
 
 instance Alternative ParseS where
diff --git a/src/Lambdabot/Plugin/Haskell/Pl/Transform.hs b/src/Lambdabot/Plugin/Haskell/Pl/Transform.hs
--- a/src/Lambdabot/Plugin/Haskell/Pl/Transform.hs
+++ b/src/Lambdabot/Plugin/Haskell/Pl/Transform.hs
@@ -55,7 +55,9 @@
 unLet (Lambda v e) = Lambda v (unLet e)
 unLet (Var f x) = Var f x
 
-type Env = M.Map String String
+type Env = (M.Map String String, Int)
+-- note: The second component is the environment size, counting duplicate
+-- variables.
 
 -- | Rename all variables to (locally) unique fresh ones
 --
@@ -63,9 +65,9 @@
 -- Otherwise a newly created id/const/... could be bound by a lambda
 -- e.g. transform' (\id x -> x) ==> transform' (\id -> id) ==> id
 alphaRename :: Expr -> Expr
-alphaRename e = alpha e `evalState` M.empty where
+alphaRename e = alpha e `evalState` (M.empty, 0) where
   alpha :: Expr -> State Env Expr
-  alpha (Var f v)     = do fm <- get; return $ Var f $ maybe v id (M.lookup v fm)
+  alpha (Var f v)     = do (fm, _) <- get; return $ Var f $ maybe v id (M.lookup v fm)
   alpha (App e1 e2)   = liftM2 App (alpha e1) (alpha e2)
   alpha (Let _ _)     = assert False undefined
   alpha (Lambda v e') = inEnv $ liftM2 Lambda (alphaPat v) (alpha e')
@@ -75,9 +77,9 @@
   inEnv f = state $ \s -> (fst $ runState f s, s)
 
   alphaPat (PVar v) = do
-    fm <- get
-    let v' = "$" ++ show (M.size fm)
-    put $ M.insert v v' fm
+    (fm, i) <- get
+    let v' = "$" ++ show i
+    put (M.insert v v' fm, i+1)
     return $ PVar v'
   alphaPat (PTuple p1 p2) = liftM2 PTuple (alphaPat p1) (alphaPat p2)
   alphaPat (PCons  p1 p2) = liftM2 PCons  (alphaPat p1) (alphaPat p2)
diff --git a/src/Lambdabot/Plugin/Haskell/Pointful.hs b/src/Lambdabot/Plugin/Haskell/Pointful.hs
--- a/src/Lambdabot/Plugin/Haskell/Pointful.hs
+++ b/src/Lambdabot/Plugin/Haskell/Pointful.hs
@@ -194,7 +194,7 @@
     b
 -- replace (\x -> \y -> z) with (\x y -> z)
 optimizeE (Lambda p1 (Lambda p2 body)) =
-    let (subst, bv, p2') = renameBinds M.empty (varsBoundHere p1) p2
+    let (subst, bv, p2') = renameBinds M.empty (freeVars (Lambda p2 body)) p2
         body' = substAvoiding subst bv body
     in  Lambda (p1 ++ p2') body'
 -- remove double parens
diff --git a/src/Lambdabot/Plugin/Haskell/UnMtl.hs b/src/Lambdabot/Plugin/Haskell/UnMtl.hs
--- a/src/Lambdabot/Plugin/Haskell/UnMtl.hs
+++ b/src/Lambdabot/Plugin/Haskell/UnMtl.hs
@@ -164,17 +164,17 @@
     hsMod <- liftE $ parseModule ("type X = " ++ input ++ "\n")
     decls <- case hsMod of
         (Hs.Module _ _ _ decls) -> return decls
-        _ -> fail "Not a module?"
+        _ -> Left "Not a module?"
     hsType <- case decls of
         (TypeDecl _ hsType:_) -> return hsType
-        _ -> fail "No parse?"
+        _ -> Left "No parse?"
     let result = mtlParser' hsType
     case pError result of
-        Just e  -> fail e
+        Just e  -> Left e
         Nothing -> return (pResult result)
   where
     liftE (ParseOk a) = return a
-    liftE (ParseFailed _src str) = fail str
+    liftE (ParseFailed _src str) = Left str
 
 mtlParser' :: Type -> PType
 mtlParser' t@(TyCon (UnQual (Ident v))) = case lookup v types of