diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+# 3.3.0.4
+
+  * Don't crash when deduplicating tuples, arrays, optional values
+
 # 3.3.0.3
 
   * Fix splitting with `--header` on large inputs
diff --git a/examples/evenOdd.jac b/examples/evenOdd.jac
new file mode 100644
--- /dev/null
+++ b/examples/evenOdd.jac
@@ -0,0 +1,14 @@
+fn count(x) ≔
+  fold (+) 0 (([:1)"x);
+
+fn isEven() :=
+  (~ /(0|2|4|6|8)$/);
+
+fn isOdd() :=
+  (~ /(1|3|5|7|9)$/);
+
+let
+  val even := count (isEven #. $0)
+  val odd := count (isOdd #. $0)
+  val total := odd + even
+in (total . even . odd) end
diff --git a/examples/path.jac b/examples/path.jac
--- a/examples/path.jac
+++ b/examples/path.jac
@@ -1,4 +1,5 @@
 {. echo $PATH | ja run examples/path.jac
+{. ja run examples/path.jac <(echo $PATH)
 fn path(x) :=
   ([x+'\n'+y]) |> (splitc x ':');
 
diff --git a/examples/pubmed2tex.jac b/examples/pubmed2tex.jac
--- a/examples/pubmed2tex.jac
+++ b/examples/pubmed2tex.jac
@@ -1,5 +1,6 @@
 {. ja run pubmed2tex.jac -i citation.nbib
-:set rs:=/\r\n/;
+:set header;
+:set rs:=/\r\n[A-Z]{2,4}/;
 
 {. 10.1016/j.tig.2011.10.004 [doi]
 fn doi(record) :=
@@ -12,7 +13,7 @@
   '    ' + label + '={' + r + '},';
 
 fn collateAu(r) :=
-  r ~* 1 /^FAU - (.*)$/;
+  r ~* 1 /FAU - (.*)$/;
 
 fn bind(f,x) :=
   option None f x;
@@ -21,8 +22,8 @@
 
 fn field(r) :=
   let 
-    val key := r ~* 1 /^([A-Z ]{4})-/
-    val value := r ~* 2 /^([A-Z ]{4})-\s*(.*)/
+    val key := r ~* 1 /([A-Z ]{4})-/
+    val value := r ~* 2 /([A-Z ]{4})-\s*(.*)/
   in
      ?key=Some 'TI  ';(pfield 'title')¨value
     ;?key=Some 'AID ';(pfield 'doi')¨bind doi value
diff --git a/examples/tagsex.jac b/examples/tagsex.jac
new file mode 100644
--- /dev/null
+++ b/examples/tagsex.jac
@@ -0,0 +1,12 @@
+fn mkEx(s) :=
+  '/^' + s + '$/;';
+
+{. TODO: insert \zs at precise identifier! https://stackoverflow.com/a/31089753/11296354
+
+fn processStr(s) :=
+  let
+    val line := split s /[ \(:]+/
+    val outLine := sprintf '%s\t%s\t%s' (line.3 . fp . mkEx s)
+  in outLine end;
+
+processStr¨{%/fn +[[:lower:]][[:latin:]]*.*:=/}{`0}
diff --git a/examples/tastyStackTrace.jac b/examples/tastyStackTrace.jac
new file mode 100644
--- /dev/null
+++ b/examples/tastyStackTrace.jac
@@ -0,0 +1,5 @@
+{. ja run examples/tastyStackTrace.jac -Dm='/Ty/' -i test/data/tasty-prof
+:set rs:=/\*\*\* Exception \(reporting due to \+RTS \-xc\): \(THUNK(_\d)*\), stack trace:/;
+:set fs:=/\n/;
+
+{%m}{[x+'\n'+y]|>[x !~ /Test\.Tasty/] #. `$}
diff --git a/jacinda.cabal b/jacinda.cabal
--- a/jacinda.cabal
+++ b/jacinda.cabal
@@ -1,6 +1,6 @@
 cabal-version:      2.2
 name:               jacinda
-version:            3.3.0.3
+version:            3.3.0.4
 license:            AGPL-3.0-only
 license-file:       COPYING
 maintainer:         vamchale@gmail.com
@@ -18,9 +18,7 @@
     lib/fs/*.jac
     prelude/*.jac
 
-extra-doc-files:
-    CHANGELOG.md
-
+extra-doc-files:    CHANGELOG.md
 extra-source-files:
     README.md
     man/ja.1
@@ -63,14 +61,14 @@
 
 common warnings
     ghc-options:
-        -Wall
-        -Wincomplete-uni-patterns -Wincomplete-record-updates
+        -Wall -Wincomplete-uni-patterns -Wincomplete-record-updates
         -Wredundant-constraints -Widentities -Wcpp-undef
         -Wmissing-export-lists -Wunused-packages -Wno-x-partial
         -Wno-missing-signatures -Wredundant-bang-patterns
+        -Wno-operator-whitespace-ext-conflict
 
 library jacinda-lib
-    import:           warnings
+    import:             warnings
     exposed-modules:
         File
         A
@@ -78,7 +76,7 @@
         Parser
         Jacinda.Regex
 
-    hs-source-dirs:   src
+    hs-source-dirs:     src
     other-modules:
         A.I
         A.E
@@ -99,20 +97,20 @@
         C
         Paths_jacinda
 
-    autogen-modules:  Paths_jacinda
-    default-language: Haskell2010
-    ghc-options:      -O2
+    autogen-modules:    Paths_jacinda
+    default-language:   Haskell2010
+    ghc-options:        -O2
     build-depends:
         base >=4.11.0.0 && <5,
         bytestring >=0.11.2.0,
         dlist,
-        text,
+        text >=2.0.1,
         prettyprinter >=1.7.0,
         containers >=0.6.0.1,
         array,
         mtl,
         transformers,
-        regex-rure >=0.1.2.0,
+        regex-rure >=0.1.2.0 && <1.0.0.0,
         microlens,
         directory,
         filepath,
@@ -135,7 +133,9 @@
         OverloadedLists
 
     if !flag(cross)
-        build-tool-depends: alex:alex >=3.5.0.0, happy:happy >=2.1
+        build-tool-depends:
+            , alex:alex    >=3.5.0.0
+            , happy:happy  >=2.1
 
 executable ja
     import:           warnings
@@ -146,11 +146,11 @@
     default-language: Haskell2010
     ghc-options:      -rtsopts "-with-rtsopts=-A200k -k32k"
     build-depends:
-        base,
-        directory,
-        jacinda-lib,
-        optparse-applicative >=0.14.1.0,
-        text
+        , base
+        , directory
+        , jacinda-lib
+        , optparse-applicative  >=0.14.1.0
+        , text
 
 test-suite jacinda-test
     import:           warnings
@@ -160,14 +160,14 @@
     default-language: Haskell2010
     ghc-options:      -threaded -rtsopts "-with-rtsopts=-N -K1K"
     build-depends:
-        base,
-        jacinda-lib,
-        bytestring,
-        tasty,
-        tasty-golden,
-        tasty-hunit,
-        temporary,
-        text
+        , base
+        , bytestring
+        , jacinda-lib
+        , tasty
+        , tasty-golden
+        , tasty-hunit
+        , temporary
+        , text
 
 benchmark jacinda-bench
     import:           warnings
diff --git a/src/A.hs b/src/A.hs
--- a/src/A.hs
+++ b/src/A.hs
@@ -55,14 +55,14 @@
 
 infixr 0 :$
 
-data T = TyB { tyBuiltin :: TB }
+data T = TyB { tyBuiltin :: !TB }
        | (:$) { tyApp0, tyApp1 :: T }
        | TyArr { tyArr0, tyArr1 :: T }
-       | TyVar { tyVar :: Nm () }
+       | TyVar { tyVar :: !(Nm ()) }
        | TyTup { tyTups :: [T] }
        | TyRec { tyres :: NmMap T }
-       | Rho { tyRho :: Nm (), tyArms :: IM.IntMap T }
-       | Ρ { tyΡ :: Nm (), tyρs :: NmMap T }
+       | Rho { tyRho :: !(Nm ()), tyArms :: IM.IntMap T }
+       | Ρ { tyΡ :: !(Nm ()), tyρs :: NmMap T }
        deriving Eq
 
 instance Pretty TB where
@@ -180,14 +180,30 @@
 -- 0-ary
 data N = Ix | Nf | None | Fp | MZ
 
-data L = ILit !Integer | FLit !Double | BLit !Bool | StrLit BS.ByteString deriving (Generic, NFData)
+data L = ILit !Integer | FLit !Double | BLit !Bool | StrLit BS.ByteString deriving (Generic, Eq, Ord, NFData)
 
 class PS a where ps :: Int -> a -> Doc ann
 
+instance Eq (E a) where
+    (==) (Lit _ l₀) (Lit _ l₁)             = l₀==l₁
+    (==) (Tup _ es₀) (Tup _ es₁)           = es₀==es₁
+    (==) (Rec _ a₀) (Rec _ a₁)             = a₀==a₁
+    (==) (OptionVal _ e₀) (OptionVal _ e₁) = e₀==e₁
+    (==) (Arr _ e₀) (Arr _ e₁)             = e₀==e₁
+    (==) _ _                               = undefined
+
+instance Ord (E a) where
+    compare (Lit _ l₀) (Lit _ l₁)             = compare l₀ l₁
+    compare (Tup _ es₀) (Tup _ es₁)           = compare es₀ es₁
+    compare (Rec _ a₀) (Rec _ a₁)             = compare a₀ a₁
+    compare (OptionVal _ e₀) (OptionVal _ e₁) = compare e₀ e₁
+    compare (Arr _ e₀) (Arr _ e₁)             = compare e₀ e₁
+    compare _ _                               = undefined
+
 -- expression
-data E a = Column { eLoc :: a, col :: Int }
-         | IParseCol { eLoc :: a, col :: Int } | FParseCol { eLoc :: a, col :: Int } | ParseCol { eLoc :: a, col :: Int }
-         | Field { eLoc :: a, eField :: Int } | LastField { eLoc :: a } | FieldList { eLoc :: a }
+data E a = Column { eLoc :: a, col :: !Int }
+         | IParseCol { eLoc :: a, col :: !Int } | FParseCol { eLoc :: a, col :: !Int } | ParseCol { eLoc :: a, col :: Int }
+         | Field { eLoc :: a, eField :: !Int } | LastField { eLoc :: a } | FieldList { eLoc :: a }
          | AllField { eLoc :: a } -- ^ Think @$0@ in awk.
          | AllColumn { eLoc :: a } -- ^ Think @$0@ in awk.
          | IParseAllCol { eLoc :: a } -- ^ @$0@, parsed as an integer
@@ -203,18 +219,18 @@
          | RegexLit { eLoc :: a, eRr :: BS.ByteString }
          | Lam { eLoc :: a, eBound :: Nm a, lamE :: E a }
          | Dfn { eLoc :: a, eDfn :: E a }
-         | BB { eLoc :: a, eBin :: BBin } | TB { eLoc :: a, eTer :: BTer } | UB { eLoc :: a, eUn :: BUn }
-         | NB { eLoc :: a, eNil :: N }
+         | BB { eLoc :: a, eBin :: !BBin } | TB { eLoc :: a, eTer :: !BTer } | UB { eLoc :: a, eUn :: !BUn }
+         | NB { eLoc :: a, eNil :: !N }
          | Tup { eLoc :: a, esTup :: [E a] }
          | Rec { eLoc :: a, esR :: [(Nm a, E a)] }
-         | ResVar { eLoc :: a, dfnVar :: DfnVar }
+         | ResVar { eLoc :: a, dfnVar :: !DfnVar }
          | RC RurePtr -- compiled regex after normalization
          | Arr { eLoc :: a, elems :: !(V.Vector (E a)) }
          | Anchor { eLoc :: a, eAnchored :: [E a] }
-         | Paren { eLoc :: a, eExpr :: E a }
+         | Paren { eLoc :: a, eExpr :: !(E a) }
          | OptionVal { eLoc :: a, eMaybe :: Maybe (E a) }
          | Cond { eLoc :: a, eIf, eThen, eElse :: E a }
-         | RwB { eLoc :: a, eBin :: BBin } | RwT { eLoc :: a, eTer :: BTer }
+         | RwB { eLoc :: a, eBin :: !BBin } | RwT { eLoc :: a, eTer :: !BTer }
          deriving (Functor)
 
 instance Pretty N where
@@ -332,11 +348,11 @@
 instance Show C where show=show.pretty
 
 -- decl
-data D a = SetFS T.Text | SetRS T.Text
+data D a = SetFS !T.Text | SetRS !T.Text
          | FunDecl (Nm a) [Nm a] (E a)
          | FlushDecl | SetH
          | SetAsv | SetUsv | SetCsv
-         | SetOFS T.Text | SetORS T.Text
+         | SetOFS !T.Text | SetORS !T.Text
          deriving (Functor)
 
 instance Pretty (D a) where
@@ -363,7 +379,7 @@
 
 awk = AWK Nothing Nothing False
 
-data Mode = CSV | AWK (Maybe T.Text) (Maybe T.Text) Bool -- field, record, include header in record split
+data Mode = CSV | AWK !(Maybe T.Text) !(Maybe T.Text) !Bool -- field, record, include header in record split
 
 getS :: Program a -> Mode
 getS (Program ds _) = foldl' go awk ds where
diff --git a/src/Include.hs b/src/Include.hs
--- a/src/Include.hs
+++ b/src/Include.hs
@@ -1,18 +1,18 @@
-module Include ( defaultIncludes
-               , resolveImport
-               ) where
+{-# LANGUAGE LambdaCase #-}
 
-import           Control.Exception  (Exception, throwIO)
-import           Control.Monad      (filterM)
-import           Data.List.Split    (splitWhen)
-import           Data.Maybe         (listToMaybe)
-import           Paths_jacinda      (getDataDir)
-import           System.Directory   (doesDirectoryExist, doesFileExist, getCurrentDirectory)
-import           System.Environment (lookupEnv)
-import           System.FilePath    ((</>))
+module Include ( defaultIncludes, resolveImport ) where
 
-data ImportError = FileNotFound !FilePath ![FilePath] deriving (Show)
+import           Control.Exception         (Exception, throwIO)
+import           Control.Monad             (filterM, (<=<))
+import           Data.Containers.ListUtils (nubOrd)
+import           Data.List.Split           (splitWhen)
+import           Paths_jacinda             (getDataDir)
+import           System.Directory          (canonicalizePath, doesDirectoryExist, doesFileExist, getCurrentDirectory)
+import           System.Environment        (lookupEnv)
+import           System.FilePath           ((</>))
 
+data ImportError = FileNotFound !FilePath ![FilePath] | AmbiguousInclude ![FilePath] deriving (Show)
+
 instance Exception ImportError where
 
 defaultIncludes :: IO ([FilePath] -> [FilePath])
@@ -27,13 +27,12 @@
 
 jacPath :: IO [FilePath]
 jacPath = maybe [] splitEnv <$> lookupEnv "JAC_PATH"
-
-splitEnv :: String -> [FilePath]
-splitEnv = splitWhen (== ':')
+  where
+    splitEnv = splitWhen (== ':')
 
-resolveImport :: [FilePath] -- ^ Places to look
-              -> FilePath
-              -> IO FilePath
-resolveImport incl fp =
-    maybe (throwIO $ FileNotFound fp incl) pure . listToMaybe
-        =<< (filterM doesFileExist . fmap (</> fp) $ incl)
+resolveImport :: [FilePath] -> FilePath -> IO FilePath
+resolveImport incl fp = ($incl) $
+    (\case [] -> throwIO $ FileNotFound fp incl; [src] -> pure (src</>fp); fs -> throwIO $ AmbiguousInclude fs)
+    . nubOrd
+        <=< traverse canonicalizePath
+        <=< (filterM (doesFileExist . (</> fp)))
diff --git a/src/Jacinda/Backend/T.hs b/src/Jacinda/Backend/T.hs
--- a/src/Jacinda/Backend/T.hs
+++ b/src/Jacinda/Backend/T.hs
@@ -55,13 +55,13 @@
 instance Exception StreamError where
 
 type Env = IM.IntMap (Maybe (E T)); type I=Int
-data Σ = Σ !I !Env (IM.IntMap (S.Set BS.ByteString)) (IM.IntMap IS.IntSet) (IM.IntMap (S.Set Double)) IS.IntSet
+data Σ = Σ !I !Env (IM.IntMap (S.Set BS.ByteString)) (IM.IntMap IS.IntSet) (IM.IntMap (S.Set Double)) IS.IntSet (IM.IntMap (S.Set (E T)))
 type Tmp = Int
 type Β = IM.IntMap (E T)
 
 mE :: (Env -> Env) -> Σ -> Σ
-mE f (Σ i e d di df b) = Σ i (f e) d di df b
-gE (Σ _ e _ _ _ _) = e
+mE f (Σ i e d di df b de) = Σ i (f e) d di df b de
+gE (Σ _ e _ _ _ _ _) = e
 
 at :: V.Vector a -> Int -> a
 v `at` ix = case v V.!? (ix-1) of {Just x -> x; Nothing -> throw $ IndexOutOfBounds ix}
@@ -102,19 +102,19 @@
 run h flush j e ctxs | TyB TyUnit <- eLoc e =  (\(s, f, env) -> pSF h flush (s,f) env) $ uStream j $ do
     (res, tt, iEnv, μ) <- unit e
     u <- nI
-    let outs=μ<$>ctxs; es'=scanl' (&) (Σ u iEnv IM.empty IM.empty IM.empty IS.empty) outs
+    let outs=μ<$>ctxs; es'=scanl' (&) (Σ u iEnv IM.empty IM.empty IM.empty IS.empty IM.empty) outs
     pure (res, tt, gE<$>es')
 run h flush j e ctxs | TyB TyStream:$_ <- eLoc e = traverse_ (traverse_ (pS h flush)).uStream j $ do
     t <- nI
     (iEnv, μ) <- ctx e t
     u <- nI
-    let outs=μ<$>ctxs; es={-# SCC "scanMain" #-} scanl' (&) (Σ u iEnv IM.empty IM.empty IM.empty IS.empty) outs
+    let outs=μ<$>ctxs; es={-# SCC "scanMain" #-} scanl' (&) (Σ u iEnv IM.empty IM.empty IM.empty IS.empty IM.empty) outs
     pure ((! t).gE<$>es)
 run h _ j e ctxs = pDocLn h $ uStream j $ do
     (iEnv, g, e0) <- collect e
     u <- nI
     let updates=g<$>ctxs
-        finEnv=foldl' (&) (Σ u iEnv IM.empty IM.empty IM.empty IS.empty) updates
+        finEnv=foldl' (&) (Σ u iEnv IM.empty IM.empty IM.empty IS.empty IM.empty) updates
     e0@>(fromMaybe (throw EmptyFold)<$>gE finEnv)
 
 unit :: E T -> UM (Maybe Tmp, [Tmp], Env, LineCtx -> Σ -> Σ)
@@ -276,6 +276,7 @@
 ctx (EApp _ (EApp _ (EApp _ (TB _ ZipW) op) xs) ys) o    = do {t0 <- nI; t1 <- nI; (env0, sb0) <- ctx xs t0; (env1, sb1) <- ctx ys t1; pure (na o (env0<>env1), \l->wZ op t0 t1 o.sb0 l.sb1 l)}
 ctx (EApp _ (EApp _ (BB _ Prior) op) xs) o               = do {t <- nI; (env, sb) <- ctx xs t; pt <- nI; pure (na o (pt\~env), \l -> wΠ op pt t o.sb l)}
 ctx (EApp (_:$TyB ty) (UB _ Dedup) xs) o                 = do {k <- nI; t <- nI; (env, sb) <- ctx xs t; pure (na o env, \l->wD ty k t o.sb l)}
+ctx (EApp _ (UB _ Dedup) xs) o                           = do {k <- nI; t <- nI; (env, sb) <- ctx xs t; pure (na o env, \l->wDE k t o.sb l)}
 ctx (EApp _ (EApp _ (BB _ DedupOn) f) xs) o              = do {k <- nI; t <- nI; (env, sb) <- ctx xs t; pure (na o env, \l->wDOp f k t o.sb l)}
 ctx (EApp _ (EApp _ (EApp _ (TB _ Bookend) e0) e1) xs) o = do {k <- nI; t <- nI; (env, sb) <- ctx xs t; r0 <- e0@>mempty; r1<- e1@>mempty; pure (na o env, \l->wB (r0,r1) k t o.sb l)}
 ctx e _ | TyB TyStream:$_ <- eLoc e = error ("?? uh-oh. " ++ show e)
@@ -558,70 +559,71 @@
 ms (Nm _ (U i) _) = IM.singleton i
 
 wCM :: Tmp -> Tmp -> Σ -> Σ
-wCM src tgt (Σ u env d di df b) =
+wCM src tgt (Σ u env d di df b de) =
     Σ u (case env!src of
         Just y  -> case asM y of {Nothing -> tgt\~env; Just yϵ -> env&tgt~!yϵ}
-        Nothing -> tgt\~env) d di df b
+        Nothing -> tgt\~env) d di df b de
 
 {-# SCC wMM #-}
 wMM :: E T -> Tmp -> Tmp -> Σ -> Σ
-wMM (Lam _ n e) src tgt (Σ j env d di df b) =
+wMM (Lam _ n e) src tgt (Σ j env d di df b de) =
     case env!src of
         Just x ->
             let be=ms n x; (y,k)=e@!(j,be)
             in Σ k (case asM y of
                 Just yϵ -> env&tgt~!yϵ
-                Nothing -> tgt\~env) d di df b
-        Nothing -> Σ j (tgt\~env) d di df b
+                Nothing -> tgt\~env) d di df b de
+        Nothing -> Σ j (tgt\~env) d di df b de
 wMM e _ _ _ = throw$InternalArityOrEta 1 e
 
 wZ :: E T -> Tmp -> Tmp -> Tmp -> Σ -> Σ
-wZ (Lam _ n0 (Lam _ n1 e)) src0 src1 tgt (Σ j env d di df b) =
+wZ (Lam _ n0 (Lam _ n1 e)) src0 src1 tgt (Σ j env d di df b de) =
     (case (env!src0, env!src1) of
         (Just x, Just y) ->
             let be=me [(n0, x), (n1, y)]; (z,k)=e@!(j,be)
             in Σ k (env&tgt~!z)
-        (Nothing, Nothing) -> Σ j (tgt\~env)) d di df b
+        (Nothing, Nothing) -> Σ j (tgt\~env)) d di df b de
 wZ e _ _ _ _ = throw$InternalArityOrEta 2 e
 
 wM :: E T -> Tmp -> Tmp -> Σ -> Σ
-wM (Lam _ n e) src tgt (Σ j env d di df b) =
+wM (Lam _ n e) src tgt (Σ j env d di df b de) =
     case env!src of
         Just x ->
             let be=ms n x; (y,k)=e@!(j,be)
-            in Σ k (env&tgt~!y) d di df b
-        Nothing -> Σ j (tgt\~env) d di df b
+            in Σ k (env&tgt~!y) d di df b de
+        Nothing -> Σ j (tgt\~env) d di df b de
 wM e _ _ _ = throw$InternalArityOrEta 1 e
 
 wI :: E T -> Tmp -> LineCtx -> Σ -> Σ
-wI e tgt line (Σ j env d di df b) =
-    let e'=e `κ` line; (e'',k)=e'$@j in Σ k (env&tgt~!e'') d di df b
+wI e tgt line (Σ j env d di df b de) =
+    let e'=e `κ` line; (e'',k)=e'$@j in Σ k (env&tgt~!e'') d di df b de
 
 wG :: (E T, E T) -> Tmp -> LineCtx -> Σ -> Σ
-wG (p, e) tgt line (Σ j env d di df b) =
+wG (p, e) tgt line (Σ j env d di df b de) =
     let p'=p `κ` line; (p'',k)=p'$@j
     in (if asB p''
         then let e'=e `κ` line; (e'',u) =e'$@k in Σ u (env&tgt~!e'')
-        else Σ k (tgt\~env)) d di df b
+        else Σ k (tgt\~env)) d di df b de
 
+-- TODO: TyBool
 wDOp :: E T -> Int -> Tmp -> Tmp -> Σ -> Σ
-wDOp (Lam (TyArr _ (TyB TyStr)) n e) key src tgt (Σ i env d di df b) =
+wDOp (Lam (TyArr _ (TyB TyStr)) n e) key src tgt (Σ i env d di df b de) =
     case env!src of
-        Nothing -> Σ i (tgt\~env) d di df b
+        Nothing -> Σ i (tgt\~env) d di df b de
         Just xϵ ->
             case IM.lookup key d of
-                Nothing -> Σ k (env&tgt~!y) (IM.insert key (S.singleton e') d) di df b
-                Just ss -> (if e' `S.member` ss then Σ k (tgt\~env) d else Σ k (env&tgt~!y) (key!:e'$d)) di df b
+                Nothing -> Σ k (env&tgt~!y) (IM.insert key (S.singleton e') d) di df b de
+                Just ss -> (if e' `S.member` ss then Σ k (tgt\~env) d else Σ k (env&tgt~!y) (key!:e'$d)) di df b de
               where
                 (y,k)=e@!(i,be); be=ms n xϵ
                 e'=asS y
-wDOp (Lam (TyArr _ (TyB TyI)) n e) key src tgt (Σ i env d di df b) =
+wDOp (Lam (TyArr _ (TyB TyI)) n e) key src tgt (Σ i env d di df b de) =
     case env!src of
-        Nothing -> Σ i (tgt\~env) d di df b
+        Nothing -> Σ i (tgt\~env) d di df b de
         Just xϵ ->
             case IM.lookup key di of
-                Nothing -> Σ k (env&tgt~!y) d (IM.insert key (IS.singleton e') di) df b
-                Just ds -> (if e' `IS.member` ds then Σ k (tgt\~env) d di else Σ k (env&tgt~!y) d (IM.alter go key di)) df b
+                Nothing -> Σ k (env&tgt~!y) d (IM.insert key (IS.singleton e') di) df b de
+                Just ds -> (if e' `IS.member` ds then Σ k (tgt\~env) d di else Σ k (env&tgt~!y) d (IM.alter go key di)) df b de
 
               where
                 (y,k)=e@!(i,be); be=ms n xϵ
@@ -629,16 +631,25 @@
 
                 go Nothing  = Just$!IS.singleton e'
                 go (Just s) = Just$!IS.insert e' s
-wDOp (Lam (TyArr _ (TyB TyFloat)) n e) key src tgt (Σ i env d di df b) =
+wDOp (Lam (TyArr _ (TyB TyFloat)) n e) key src tgt (Σ i env d di df b de) =
     case env!src of
-        Nothing -> Σ i (tgt\~env) d di df b
+        Nothing -> Σ i (tgt\~env) d di df b de
         Just xϵ ->
             case IM.lookup key df of
-                Nothing -> Σ k (env&tgt~!y) d di (IM.insert key (S.singleton e') df) b
-                Just ds -> if e' `S.member` ds then Σ k (tgt\~env) d di df b else Σ k (env&tgt~!y) d di (key!:e'$df) b
+                Nothing -> Σ k (env&tgt~!y) d di (IM.insert key (S.singleton e') df) b de
+                Just ds -> (if e' `S.member` ds then Σ k (tgt\~env) d di df else Σ k (env&tgt~!y) d di (key!:e'$df)) b de
               where
                 (y,k)=e@!(i,be); be=ms n xϵ
                 e'=asF y
+wDOp (Lam _ n e) key src tgt (Σ i env d di df b de) =
+    case env!src of
+        Nothing -> Σ i (tgt\~env) d di df b de
+        Just xϵ ->
+            case IM.lookup key de of
+                Nothing -> Σ k (env&tgt~!y) d di df b (IM.insert key (S.singleton y) de)
+                Just ds -> (if y `S.member` ds then Σ k (tgt\~env) d di df b de else Σ k (env&tgt~!y) d di df b (key!:y$de))
+              where
+                (y,k)=e@!(i,be); be=ms n xϵ
 wDOp e _ _ _ _ = throw $ InternalArityOrEta 1 e
 
 (\~) k = IM.insert k Nothing
@@ -647,60 +658,70 @@
 (!:) k e = IM.alter (\x -> Just$!case x of Nothing -> S.singleton e; Just s -> S.insert e s) k
 
 wB :: (E T, E T) -> Int -> Tmp -> Tmp -> Σ -> Σ
-wB (e0, e1) key src tgt (Σ i env d di df b) =
-    case env!src of
+wB (e0, e1) key src tgt (Σ i env d di df b de) =
+    (case env!src of
         Nothing -> Σ i (tgt\~env) d di df b
         Just xϵ -> let xS=asS xϵ in if key `IS.member` b
-            then if isMatch' r1 xS then Σ i (env&tgt~!xϵ) d di df (IS.delete key b) else Σ i (env&tgt~!xϵ) d di df b
-            else if isMatch' r0 xS then Σ i (env&tgt~!xϵ) d di df (IS.insert key b) else Σ i (tgt\~env) d di df b
+            then (if isMatch' r1 xS then Σ i (env&tgt~!xϵ) d di df (IS.delete key b) else Σ i (env&tgt~!xϵ) d di df b)
+            else (if isMatch' r0 xS then Σ i (env&tgt~!xϵ) d di df (IS.insert key b) else Σ i (tgt\~env) d di df b)) de
   where
     r0=asR e0; r1=asR e1
 
+wDE :: Int -> Tmp -> Tmp -> Σ -> Σ
+wDE key src tgt (Σ i env d di df b de) =
+    case env!src of
+        Nothing -> Σ i (tgt\~env) d di df b de
+        Just e ->
+            case IM.lookup key de of
+                Nothing -> Σ i (env&tgt~!e) d di df b (IM.insert key (S.singleton e) de)
+                Just ds -> if e `S.member` ds then Σ i (tgt\~env) d di df b de else Σ i (env&tgt~!e) d di df b (key!:e$de)
+
+-- TODO: TyB lol
 {-# SCC wD #-}
 wD :: TB -> Int -> Tmp -> Tmp -> Σ -> Σ
-wD TyStr key src tgt (Σ i env d di df b) =
+wD TyStr key src tgt (Σ i env d di df b de) =
     case env!src of
-        Nothing -> Σ i (tgt\~env) d di df b
+        Nothing -> Σ i (tgt\~env) d di df b de
         Just e ->
             case IM.lookup key d of
-                Nothing -> Σ i (env&tgt~!e) (IM.insert key (S.singleton e') d) di df b
-                Just ds -> (if e' `S.member` ds then Σ i (tgt\~env) d else Σ i (env&tgt~!e) (key!:e'$d)) di df b
+                Nothing -> Σ i (env&tgt~!e) (IM.insert key (S.singleton e') d) di df b de
+                Just ds -> (if e' `S.member` ds then Σ i (tgt\~env) d else Σ i (env&tgt~!e) (key!:e'$d)) di df b de
               where
                 e'=asS e
-wD TyI key src tgt (Σ i env d di df b) =
+wD TyI key src tgt (Σ i env d di df b de) =
     case env!src of
-        Nothing -> Σ i (tgt\~env) d di df b
+        Nothing -> Σ i (tgt\~env) d di df b de
         Just e ->
             case IM.lookup key di of
-                Nothing -> Σ i (env&tgt~!e) d (IM.insert key (IS.singleton e') di) df b
-                Just ds -> (if e' `IS.member` ds then Σ i (tgt\~env) d di else Σ i (env&tgt~!e) d (IM.alter go key di)) df b
+                Nothing -> Σ i (env&tgt~!e) d (IM.insert key (IS.singleton e') di) df b de
+                Just ds -> (if e' `IS.member` ds then Σ i (tgt\~env) d di else Σ i (env&tgt~!e) d (IM.alter go key di)) df b de
               where
                 e'=fromIntegral$asI e
 
                 go Nothing  = Just$!IS.singleton e'
                 go (Just s) = Just$!IS.insert e' s
-wD TyFloat key src tgt (Σ i env d di df b) =
+wD TyFloat key src tgt (Σ i env d di df b de) =
     case env!src of
-        Nothing -> Σ i (tgt\~env) d di df b
+        Nothing -> Σ i (tgt\~env) d di df b de
         Just e ->
             case IM.lookup key df of
-                Nothing -> Σ i (env&tgt~!e) d di (IM.insert key (S.singleton e') df) b
-                Just ds -> (if e' `S.member` ds then Σ i (tgt\~env) d di df else Σ i (env&tgt~!e) d di (key!:e'$df)) b
+                Nothing -> Σ i (env&tgt~!e) d di (IM.insert key (S.singleton e') df) b de
+                Just ds -> (if e' `S.member` ds then Σ i (tgt\~env) d di df else Σ i (env&tgt~!e) d di (key!:e'$df)) b de
               where
                 e'=asF e
 
 
 wP :: E T -> Tmp -> Tmp -> Σ -> Σ
-wP (Lam _ n e) src tgt (Σ j env d di df b) =
+wP (Lam _ n e) src tgt (Σ j env d di df b de) =
     case env!src of
         Just x ->
             let be=ms n x; (p,k)=e@!(j,be)
-            in Σ k (IM.insert tgt (if asB p then Just$!x else Nothing) env) d di df b
-        Nothing -> Σ j (tgt\~env) d di df b
+            in Σ k (IM.insert tgt (if asB p then Just$!x else Nothing) env) d di df b de
+        Nothing -> Σ j (tgt\~env) d di df b de
 wP e _ _ _ = throw $ InternalArityOrEta 1 e
 
 wΠ :: E T -> Tmp -> Tmp -> Tmp -> Σ -> Σ
-wΠ (Lam _ nn (Lam _ nprev e)) pt src tgt (Σ j env d di df b) =
+wΠ (Lam _ nn (Lam _ nprev e)) pt src tgt (Σ j env d di df b de) =
     (case (env!pt, env!src) of
         (Just prev, Just x) ->
             let be=me [(nprev, prev), (nn, x)]
@@ -708,12 +729,12 @@
             in Σ u (IM.insert pt (Just$!x) (IM.insert tgt (Just$!res) env))
         (Nothing, Nothing) -> Σ j (tgt\~env)
         (Nothing, Just x) -> Σ j (pt~!x$tgt\~env)
-        (Just{}, Nothing) -> Σ j (tgt\~env)) d di df b
+        (Just{}, Nothing) -> Σ j (tgt\~env)) d di df b de
 wΠ e _ _ _ _ = throw $ InternalArityOrEta 2 e
 
 {-# SCC wF #-}
 wF :: E T -> Tmp -> Tmp -> Σ -> Σ
-wF (Lam _ nacc (Lam _ nn e)) src tgt (Σ j env d di df b) =
+wF (Lam _ nacc (Lam _ nn e)) src tgt (Σ j env d di df b de) =
     (case (env!tgt, env!src) of
         (Just acc, Just x) ->
             let be=me [(nacc, acc), (nn, x)]
@@ -721,7 +742,7 @@
             in Σ u (env&tgt~!res)
         (Just acc, Nothing) -> Σ j (env&tgt~!acc)
         (Nothing, Nothing) -> Σ j (tgt\~env)
-        (Nothing, Just x) -> Σ j (env&tgt~!x)) d di df b
+        (Nothing, Just x) -> Σ j (env&tgt~!x)) d di df b de
 wF e _ _ _ = throw $ InternalArityOrEta 2 e
 
 badctx e = error ("Internal error: κ called on" ++ show e)
diff --git a/src/Jacinda/Regex.hs b/src/Jacinda/Regex.hs
--- a/src/Jacinda/Regex.hs
+++ b/src/Jacinda/Regex.hs
@@ -123,7 +123,7 @@
 {-# SCC splitByDL #-}
 {-# NOINLINE splitByDL #-}
 splitByDL :: RurePtr -> BS.ByteString
-          -> Maybe (DL.DList (BS.ByteString), BS.ByteString)
+          -> Maybe (DL.DList BS.ByteString, BS.ByteString)
 splitByDL _ "" = Nothing
 splitByDL re haystack@(BS.BS fp l) = bimap (fmap pp) pp <$> slicePairs
     where ixes = unsafeDupablePerformIO $ matches' re haystack
diff --git a/src/L.x b/src/L.x
--- a/src/L.x
+++ b/src/L.x
@@ -228,22 +228,18 @@
 
 constructor c t = tok (\p _ -> alex $ c p t)
 
-res = constructor TokResVar
-
-mkKw = constructor TokKeyword
-
-sym = constructor TokSym
+res = constructor TokResVar; mkKw      = constructor TokKeyword
+sym = constructor TokSym;    mkBuiltin = constructor TokBuiltin
 
-mkBuiltin = constructor TokBuiltin
+data R = Z | B
 
--- this is inefficient but w/e
 escReplace :: T.Text -> T.Text
-escReplace =
-      T.replace "\\\'" "\'"
-    . T.replace "\\\\" "\\"
-    . T.replace "\\ESC" "\ESC"
-    . T.replace "\\n" "\n"
-    . T.replace "\\t" "\t"
+escReplace = fst . T.foldl' g (T.empty, Z) where
+    g (accum, _) '\\' = (accum, B)
+    g (accum, B) '\'' = (accum `T.snoc` '\'', Z)
+    g (accum, B) 'n'  = (accum `T.snoc` '\n', Z)
+    g (accum, B) 't'  = (accum `T.snoc` '\t', Z)
+    g (accum, _) c    = (accum `T.snoc` c, Z)
 
 escRr :: T.Text -> T.Text
 escRr = T.replace "\\/" "/"
@@ -251,7 +247,6 @@
 instance Pretty AlexPosn where
     pretty (AlexPn _ line col) = pretty line <> colon <> pretty col
 
--- functional bimap?
 type AlexUserState = (Int, M.Map T.Text Int, IM.IntMap (Nm AlexPosn))
 
 alexInitUserState :: AlexUserState
diff --git a/src/Nm.hs b/src/Nm.hs
--- a/src/Nm.hs
+++ b/src/Nm.hs
@@ -12,6 +12,9 @@
 instance Eq (Nm a) where
     (==) (Nm _ u _) (Nm _ u' _) = u == u'
 
+instance Ord (Nm a) where
+    compare (Nm _ u _) (Nm _ u' _) = compare u u'
+
 instance Pretty (Nm a) where
     pretty (Nm t _ _) = pretty t
 
diff --git a/src/Nm/Map.hs b/src/Nm/Map.hs
--- a/src/Nm/Map.hs
+++ b/src/Nm/Map.hs
@@ -21,7 +21,10 @@
 infixl 9 !
 
 data NmMap a = NmMap { xx :: !(IM.IntMap a), context :: IM.IntMap T.Text }
-             deriving (Eq, Functor, Foldable, Traversable)
+             deriving (Functor, Foldable, Traversable)
+
+instance Eq a => Eq (NmMap a) where
+    (==) (NmMap xx₀ _) (NmMap xx₁ _) = xx₀==xx₁
 
 instance Semigroup (NmMap a) where
     (<>) (NmMap x y) (NmMap x' y') = NmMap (x<>x') (y<>y')
diff --git a/src/Ty.hs b/src/Ty.hs
--- a/src/Ty.hs
+++ b/src/Ty.hs
@@ -129,13 +129,15 @@
 occ (Rho (Nm _ (U i) _) rs) = IS.insert i (foldMap occ (IM.elems rs))
 occ (Ρ (Nm _ (U i) _) rs)   = IS.insert i (foldMap occ (Nm.elems rs))
 
+bc :: a -> U -> T -> T -> Subst -> Either (Err a) Subst
+bc x (U u) t t' s | u `IS.member` occ t = Left $ Occ x t t'
+                  | otherwise = Right $ IM.insert u t s
+
 mgu :: l -> Subst -> T -> T -> Either (Err l) Subst
 mgu _ s (TyB b) (TyB b') | b == b' = Right s
 mgu _ s (TyVar n) (TyVar n') | n == n' = Right s
-mgu l s t t'@(TyVar (Nm _ (U k) _)) | k `IS.notMember` occ t = Right $ IM.insert k t s
-                                      | otherwise = Left $ Occ l t' t
-mgu l s t@(TyVar (Nm _ (U k) _)) t' | k `IS.notMember` occ t' = Right $ IM.insert k t' s
-                                      | otherwise = Left $ Occ l t t'
+mgu l s t t'@(TyVar (Nm _ u _)) = bc l u t t' s
+mgu l s t@(TyVar (Nm _ u _)) t' = bc l u t' t s
 mgu l s (TyArr t0 t1) (TyArr t0' t1')  = do {s0 <- mgu l s t0 t0'; mguPrep l s0 t1 t1'}
 mgu l s (t0:$t1) (t0':$t1')            = do {s0 <- mgu l s t0 t0'; mguPrep l s0 t1 t1'}
 mgu l s (TyTup ts) (TyTup ts') | length ts == length ts' = zS (mguPrep l) s ts ts'
diff --git a/src/U.hs b/src/U.hs
--- a/src/U.hs
+++ b/src/U.hs
@@ -1,3 +1,3 @@
 module U ( U (..) ) where
 
-newtype U = U { unU :: Int } deriving (Eq)
+newtype U = U { unU :: Int } deriving (Eq, Ord)
diff --git a/test/Spec.hs b/test/Spec.hs
--- a/test/Spec.hs
+++ b/test/Spec.hs
@@ -63,6 +63,7 @@
                 awk
                 "test/data/python-site"
                 "-L/Users/vanessa/Library/Python/3.13/lib/python/site-packages -L/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/site-packages"
+          , ep "[x]~.*{ix>1}{(`4 . `5)}" CSV "test/data/food-prices.csv" "(FINAL . Dollars)"
           , harnessF "{%/hs-source-dirs/}{`2}" (AWK (Just "\\s*:\\s*") Nothing False) "jacinda.cabal" "test/golden/src-dirs.out"
           , harnessF ".?{|`0 ~* 1 /^\\s*hs-source-dirs:\\s*(.*)/}" awk "jacinda.cabal" "test/golden/src-dirs.out"
           -- , harnessF "[x+' '+y]|>$0" (AWK Nothing (Just "\\n\\s*") False) "vscode/syntaxes/jacinda.tmLanguage.json" "test/golden/minify.out"
diff --git a/test/data/12492297.nbib b/test/data/12492297.nbib
new file mode 100644
--- /dev/null
+++ b/test/data/12492297.nbib
@@ -0,0 +1,65 @@
+PMID- 12492297
+OWN - NLM
+STAT- MEDLINE
+DCOM- 20030114
+LR  - 20190910
+IS  - 0735-7044 (Print)
+IS  - 0735-7044 (Linking)
+VI  - 116
+IP  - 6
+DP  - 2002 Dec
+TI  - Organizing and activating effects of sex hormones in homosexual transsexuals.
+PG  - 982-8
+AB  - The cause of transsexualism remains unclear. The hypothesis that atypical 
+      prenatal hormone exposure could be a factor in the development of transsexualism 
+      was examined by establishing whether an atypical pattern of cognitive functioning 
+      was present in homosexual transsexuals. Possible activating effects of sex 
+      hormones as a result of cross-sex hormone treatment were also studied. 
+      Female-to-male and male-to-female transsexuals were compared with female and male 
+      controls with respect to spatial ability before and after treatment. The data 
+      were consistent with an organizing effect, but there was no evidence of an 
+      activating effect. Homosexual transsexuals, who prior to hormone treatment scored 
+      in the direction of the opposite sex, may have reached a ceiling in performance 
+      and therefore do not benefit from activating hormonal effects.
+FAU - van Goozen, Stephanie H M
+AU  - van Goozen SH
+AD  - Department of Child and Adolescent Psychiatry, University Medical Center Utrecht, 
+      The Netherlands. shmv2@cam.ac.uk
+FAU - Slabbekoorn, Ditte
+AU  - Slabbekoorn D
+FAU - Gooren, Louis J G
+AU  - Gooren LJ
+FAU - Sanders, Geoff
+AU  - Sanders G
+FAU - Cohen-Kettenis, Peggy T
+AU  - Cohen-Kettenis PT
+LA  - eng
+PT  - Journal Article
+PT  - Research Support, Non-U.S. Gov't
+PL  - United States
+TA  - Behav Neurosci
+JT  - Behavioral neuroscience
+JID - 8302411
+RN  - 0 (Gonadal Steroid Hormones)
+SB  - IM
+MH  - Adolescent
+MH  - Adult
+MH  - Cognition/*physiology
+MH  - Female
+MH  - Gonadal Steroid Hormones/*pharmacology
+MH  - Homosexuality/*psychology
+MH  - Humans
+MH  - Male
+MH  - Middle Aged
+MH  - Pregnancy
+MH  - *Prenatal Exposure Delayed Effects
+MH  - Transsexualism/*physiopathology
+EDAT- 2002/12/21 04:00
+MHDA- 2003/01/15 04:00
+CRDT- 2002/12/21 04:00
+PHST- 2002/12/21 04:00 [pubmed]
+PHST- 2003/01/15 04:00 [medline]
+PHST- 2002/12/21 04:00 [entrez]
+AID - 10.1037//0735-7044.116.6.982 [doi]
+PST - ppublish
+SO  - Behav Neurosci. 2002 Dec;116(6):982-8. doi: 10.1037//0735-7044.116.6.982.
diff --git a/test/data/3282489.nbib b/test/data/3282489.nbib
new file mode 100644
--- /dev/null
+++ b/test/data/3282489.nbib
@@ -0,0 +1,68 @@
+PMID- 3282489
+OWN - NLM
+STAT- MEDLINE
+DCOM- 19880526
+LR  - 20190919
+IS  - 0004-0002 (Print)
+IS  - 0004-0002 (Linking)
+VI  - 17
+IP  - 1
+DP  - 1988 Feb
+TI  - Neuroendocrine response to estrogen and brain differentiation in heterosexuals, 
+      homosexuals, and transsexuals.
+PG  - 57-75
+AB  - Since 1964, we have found positive estrogen feedback to be a relatively 
+      sex-specific reaction of the hypothalamo-hypophyseal system in rats as well as in 
+      human beings. It is dependent on the estrogen-convertible androgen level during 
+      sexual brain differentiation and also on estrogen priming in adulthood. The lower 
+      the estrogen-convertible androgen or primary estrogen level during brain 
+      differentiation, the higher the evocability of a positive estrogen action on LH 
+      secretion in later life. In clinical studies, we induced a positive estrogen 
+      feedback luteinizing hormone secretion in most intact homosexual men, in 
+      clear-cut contrast to intact heterosexual or bisexual men. In addition, the 
+      evocability of a positive estrogen feedback was also demonstrable in most 
+      homosexual male-to-female transsexuals in significant contrast to hetero-or 
+      bisexual male-to-female transsexuals. The following relations have been found 
+      between sex hormone levels during brain differentiation and sex-specific 
+      responses in adulthood: (i) Estrogens, which are mostly converted from androgens, 
+      are responsible for the sex-specific organization of gonadotropin secretion and 
+      hence the evocability of a positive estrogen feedback in later life; (ii) both 
+      estrogens and androgens, occurring during brain differentiation, predetermine 
+      sexual orientation, and (iii) androgens, without conversion to estrogens, are 
+      responsible for the sex-specific organization of gender role behavior. 
+      Furthermore, the organization periods for sex-specific gonadotropin secretion, 
+      sexual orientation, and gender role behavior are not identical but overlapping. 
+      Thus, combinations as well as dissociations between deviation of the 
+      neuroendocrine organization of sex-specific gonadotropin secretion, sexual 
+      orientation, and gender role behavior may occur.
+FAU - Dörner, G
+AU  - Dörner G
+LA  - eng
+PT  - Journal Article
+PT  - Review
+PL  - United States
+TA  - Arch Sex Behav
+JT  - Archives of sexual behavior
+JID - 1273516
+RN  - 0 (Estrogens)
+RN  - 9002-67-9 (Luteinizing Hormone)
+SB  - IM
+MH  - Brain/*embryology
+MH  - Estrogens/*physiology
+MH  - Feedback
+MH  - *Homosexuality
+MH  - Humans
+MH  - Luteinizing Hormone/blood
+MH  - Male
+MH  - *Sex Differentiation
+MH  - Transsexualism/*blood
+RF  - 64
+EDAT- 1988/02/01 00:00
+MHDA- 1988/02/01 00:01
+CRDT- 1988/02/01 00:00
+PHST- 1988/02/01 00:00 [pubmed]
+PHST- 1988/02/01 00:01 [medline]
+PHST- 1988/02/01 00:00 [entrez]
+AID - 10.1007/BF01542052 [doi]
+PST - ppublish
+SO  - Arch Sex Behav. 1988 Feb;17(1):57-75. doi: 10.1007/BF01542052.