fix #75

src/scope.js

@@ -56,15 +56,17 @@ var Scope = {
     }
     var key = paths.shift()
     var value = getValueFromScopes(key, scopes)
-    return paths.reduce(
-      (value, key) => {
-        if (_.isNil(value)) {
-          throw new TypeError('undefined variable: ' + key)
-        }
-        return getValueFromParent(key, value)
-      },
-      value
-    )
+    if (_.isNil(value)) {
+      throw new TypeError('undefined variable: ' + key)
+    }
+    while (paths.length) {
+      key = paths.shift()
+      value = getValueFromParent(key, value)
+      if (_.isNil(value)) {
+        throw new TypeError('undefined variable: ' + key)
+      }
+    }
+    return value
   },
 
   /*