diff --git a/lib/hyperscript/compiler.sx b/lib/hyperscript/compiler.sx
index c196eec6..c7549d51 100644
--- a/lib/hyperscript/compiler.sx
+++ b/lib/hyperscript/compiler.sx
@@ -1059,9 +1059,16 @@
                         (quote hs-method-call)
                         (cons obj (cons method args))))
                     (if
-                      (and (list? dot-node) (= (first dot-node) (quote ref)))
-                      (list (quote hs-win-call) (nth dot-node 1) (cons (quote list) args))
-                      (cons (quote hs-method-call) (cons (hs-to-sx dot-node) args))))))
+                      (and
+                        (list? dot-node)
+                        (= (first dot-node) (quote ref)))
+                      (list
+                        (quote hs-win-call)
+                        (nth dot-node 1)
+                        (cons (quote list) args))
+                      (cons
+                        (quote hs-method-call)
+                        (cons (hs-to-sx dot-node) args))))))
               ((= head (quote string-postfix))
                 (list (quote str) (hs-to-sx (nth ast 1)) (nth ast 2)))
               ((= head (quote block-literal))
@@ -1231,7 +1238,12 @@
                 (list (quote hs-coerce) (hs-to-sx (nth ast 1)) (nth ast 2)))
               ((= head (quote in?))
                 (list
-                  (quote hs-contains?)
+                  (quote hs-in?)
+                  (hs-to-sx (nth ast 2))
+                  (hs-to-sx (nth ast 1))))
+              ((= head (quote in-bool?))
+                (list
+                  (quote hs-in-bool?)
                   (hs-to-sx (nth ast 2))
                   (hs-to-sx (nth ast 1))))
               ((= head (quote of))
@@ -1717,7 +1729,16 @@
                         (rest (reverse compiled)))
                       (let
                         ((defs (filter (fn (c) (and (list? c) (> (len c) 0) (= (first c) (quote define)))) compiled))
-                          (non-defs (filter (fn (c) (not (and (list? c) (> (len c) 0) (= (first c) (quote define))))) compiled)))
+                          (non-defs
+                            (filter
+                              (fn
+                                (c)
+                                (not
+                                  (and
+                                    (list? c)
+                                    (> (len c) 0)
+                                    (= (first c) (quote define)))))
+                              compiled)))
                         (cons (quote do) (append defs non-defs)))))))
               ((= head (quote wait)) (list (quote hs-wait) (nth ast 1)))
               ((= head (quote wait-for)) (emit-wait-for ast))
@@ -1826,8 +1847,12 @@
                         (make-symbol raw-fn)
                         (hs-to-sx raw-fn)))
                     (args (map hs-to-sx (rest (rest ast)))))
-                  (if (and (list? raw-fn) (= (first raw-fn) (quote ref)))
-                    (list (quote hs-win-call) (nth raw-fn 1) (cons (quote list) args))
+                  (if
+                    (and (list? raw-fn) (= (first raw-fn) (quote ref)))
+                    (list
+                      (quote hs-win-call)
+                      (nth raw-fn 1)
+                      (cons (quote list) args))
                     (cons fn-expr args))))
               ((= head (quote return))
                 (let
@@ -2098,7 +2123,7 @@
                     (hs-to-sx (nth ast 1)))))
               ((= head (quote in?))
                 (list
-                  (quote hs-contains?)
+                  (quote hs-in?)
                   (hs-to-sx (nth ast 2))
                   (hs-to-sx (nth ast 1))))
               ((= head (quote type-check))
diff --git a/lib/hyperscript/parser.sx b/lib/hyperscript/parser.sx
index d01289a5..0c337953 100644
--- a/lib/hyperscript/parser.sx
+++ b/lib/hyperscript/parser.sx
@@ -495,7 +495,8 @@
                             (quote and)
                             (list (quote >=) left lo)
                             (list (quote <=) left hi)))))
-                    ((match-kw "in") (list (quote in?) left (parse-expr)))
+                    ((match-kw "in")
+                      (list (quote in-bool?) left (parse-expr)))
                     ((match-kw "really")
                       (do
                         (match-kw "equal")
@@ -571,7 +572,8 @@
                           (let
                             ((right (parse-expr)))
                             (list (quote not) (list (quote =) left right))))))
-                    ((match-kw "in") (list (quote in?) left (parse-expr)))
+                    ((match-kw "in")
+                      (list (quote in-bool?) left (parse-expr)))
                     ((match-kw "empty") (list (quote empty?) left))
                     ((match-kw "between")
                       (let
diff --git a/lib/hyperscript/runtime.sx b/lib/hyperscript/runtime.sx
index 78dea311..4daa71d9 100644
--- a/lib/hyperscript/runtime.sx
+++ b/lib/hyperscript/runtime.sx
@@ -1535,6 +1535,25 @@
                 (hs-contains? (rest collection) item))))))
       (true false))))
 
+(define
+  hs-in?
+  (fn
+    (collection item)
+    (cond
+      ((nil? collection) (list))
+      ((list? collection)
+        (cond
+          ((nil? item) (list))
+          ((list? item)
+            (filter (fn (x) (hs-contains? collection x)) item))
+          ((hs-contains? collection item) (list item))
+          (true (list))))
+      (true (list)))))
+
+(define
+  hs-in-bool?
+  (fn (collection item) (not (hs-falsy? (hs-in? collection item)))))
+
 (define
   hs-is
   (fn
diff --git a/shared/static/wasm/sx/hs-compiler.sx b/shared/static/wasm/sx/hs-compiler.sx
index c196eec6..c7549d51 100644
--- a/shared/static/wasm/sx/hs-compiler.sx
+++ b/shared/static/wasm/sx/hs-compiler.sx
@@ -1059,9 +1059,16 @@
                         (quote hs-method-call)
                         (cons obj (cons method args))))
                     (if
-                      (and (list? dot-node) (= (first dot-node) (quote ref)))
-                      (list (quote hs-win-call) (nth dot-node 1) (cons (quote list) args))
-                      (cons (quote hs-method-call) (cons (hs-to-sx dot-node) args))))))
+                      (and
+                        (list? dot-node)
+                        (= (first dot-node) (quote ref)))
+                      (list
+                        (quote hs-win-call)
+                        (nth dot-node 1)
+                        (cons (quote list) args))
+                      (cons
+                        (quote hs-method-call)
+                        (cons (hs-to-sx dot-node) args))))))
               ((= head (quote string-postfix))
                 (list (quote str) (hs-to-sx (nth ast 1)) (nth ast 2)))
               ((= head (quote block-literal))
@@ -1231,7 +1238,12 @@
                 (list (quote hs-coerce) (hs-to-sx (nth ast 1)) (nth ast 2)))
               ((= head (quote in?))
                 (list
-                  (quote hs-contains?)
+                  (quote hs-in?)
+                  (hs-to-sx (nth ast 2))
+                  (hs-to-sx (nth ast 1))))
+              ((= head (quote in-bool?))
+                (list
+                  (quote hs-in-bool?)
                   (hs-to-sx (nth ast 2))
                   (hs-to-sx (nth ast 1))))
               ((= head (quote of))
@@ -1717,7 +1729,16 @@
                         (rest (reverse compiled)))
                       (let
                         ((defs (filter (fn (c) (and (list? c) (> (len c) 0) (= (first c) (quote define)))) compiled))
-                          (non-defs (filter (fn (c) (not (and (list? c) (> (len c) 0) (= (first c) (quote define))))) compiled)))
+                          (non-defs
+                            (filter
+                              (fn
+                                (c)
+                                (not
+                                  (and
+                                    (list? c)
+                                    (> (len c) 0)
+                                    (= (first c) (quote define)))))
+                              compiled)))
                         (cons (quote do) (append defs non-defs)))))))
               ((= head (quote wait)) (list (quote hs-wait) (nth ast 1)))
               ((= head (quote wait-for)) (emit-wait-for ast))
@@ -1826,8 +1847,12 @@
                         (make-symbol raw-fn)
                         (hs-to-sx raw-fn)))
                     (args (map hs-to-sx (rest (rest ast)))))
-                  (if (and (list? raw-fn) (= (first raw-fn) (quote ref)))
-                    (list (quote hs-win-call) (nth raw-fn 1) (cons (quote list) args))
+                  (if
+                    (and (list? raw-fn) (= (first raw-fn) (quote ref)))
+                    (list
+                      (quote hs-win-call)
+                      (nth raw-fn 1)
+                      (cons (quote list) args))
                     (cons fn-expr args))))
               ((= head (quote return))
                 (let
@@ -2098,7 +2123,7 @@
                     (hs-to-sx (nth ast 1)))))
               ((= head (quote in?))
                 (list
-                  (quote hs-contains?)
+                  (quote hs-in?)
                   (hs-to-sx (nth ast 2))
                   (hs-to-sx (nth ast 1))))
               ((= head (quote type-check))
diff --git a/shared/static/wasm/sx/hs-parser.sx b/shared/static/wasm/sx/hs-parser.sx
index d01289a5..0c337953 100644
--- a/shared/static/wasm/sx/hs-parser.sx
+++ b/shared/static/wasm/sx/hs-parser.sx
@@ -495,7 +495,8 @@
                             (quote and)
                             (list (quote >=) left lo)
                             (list (quote <=) left hi)))))
-                    ((match-kw "in") (list (quote in?) left (parse-expr)))
+                    ((match-kw "in")
+                      (list (quote in-bool?) left (parse-expr)))
                     ((match-kw "really")
                       (do
                         (match-kw "equal")
@@ -571,7 +572,8 @@
                           (let
                             ((right (parse-expr)))
                             (list (quote not) (list (quote =) left right))))))
-                    ((match-kw "in") (list (quote in?) left (parse-expr)))
+                    ((match-kw "in")
+                      (list (quote in-bool?) left (parse-expr)))
                     ((match-kw "empty") (list (quote empty?) left))
                     ((match-kw "between")
                       (let
diff --git a/shared/static/wasm/sx/hs-runtime.sx b/shared/static/wasm/sx/hs-runtime.sx
index 78dea311..4daa71d9 100644
--- a/shared/static/wasm/sx/hs-runtime.sx
+++ b/shared/static/wasm/sx/hs-runtime.sx
@@ -1535,6 +1535,25 @@
                 (hs-contains? (rest collection) item))))))
       (true false))))
 
+(define
+  hs-in?
+  (fn
+    (collection item)
+    (cond
+      ((nil? collection) (list))
+      ((list? collection)
+        (cond
+          ((nil? item) (list))
+          ((list? item)
+            (filter (fn (x) (hs-contains? collection x)) item))
+          ((hs-contains? collection item) (list item))
+          (true (list))))
+      (true (list)))))
+
+(define
+  hs-in-bool?
+  (fn (collection item) (not (hs-falsy? (hs-in? collection item)))))
+
 (define
   hs-is
   (fn