diff --git a/whalesong/repl-compile.rkt b/whalesong/repl-compile.rkt
new file mode 100644
index 0000000..182cb12
--- /dev/null
+++ b/whalesong/repl-compile.rkt
@@ -0,0 +1,28 @@
+#lang racket/base
+
+(define this-namespace (make-base-empty-namespace))
+
+(define (make-repl-namespace [module-path 'racket/base])
+  (parameterize ([current-namespace this-namespace])
+    (dynamic-require module-path 0))
+  (define ns (make-empty-namespace))
+  (parameterize ([current-namespace ns])
+    (namespace-attach-module this-namespace module-path)  
+    (namespace-require/copy module-path))
+  ns)
+
+
+(define memoized-table (make-weak-hash))
+(define (repl-compile body #:lang [module-path 'racket/base])
+  (define key (cons body module-path))
+  (hash-ref memoized-table key (lambda ()
+                                 (parameterize ([current-namespace (make-repl-namespace module-path)])
+                                   (define compiled (compile body))
+                                   (hash-set! memoized-table key compiled)
+                                   compiled))))
+
+
+
+(for ([i 10])
+  (time (repl-compile '(* x 3) #:lang 'whalesong/lang/whalesong))
+  (time (repl-compile '(/ x 3) #:lang 'whalesong/lang/whalesong)))
diff --git a/whalesong/repl-prototype/htdocs/repl.js b/whalesong/repl-prototype/htdocs/repl.js
index d30ae0a..264c074 100644
--- a/whalesong/repl-prototype/htdocs/repl.js
+++ b/whalesong/repl-prototype/htdocs/repl.js
@@ -34,8 +34,14 @@ $(document).ready(function() {
             COMPILED.push(compiledResult);
             eval(compiledResult.compiled);
             // FIXME
-            plt.runtime.currentMachine.modules['whalesong/repl-prototype/anonymous-module.rkt'].invoke();
-            after();
+            plt.runtime.currentMachine.modules['whalesong/repl-prototype/anonymous-module.rkt'].invoke(
+                plt.runtime.currentMachine,
+                function() {
+                    after();
+                },
+                function() {
+                    after();
+                });
         };
         var onError = function(err) {
             console.log("error", err);