environment keys now include parent environments

builtin.go

@@ -228,11 +228,3 @@ var cdr = builtin{
 		return s.items[1:], nil
 	},
 }
-
-var names = builtin{
-	name:  "names",
-	arity: 0,
-	fn: func(vals []interface{}) (interface{}, error) {
-		return universe.keys(), nil
-	},
-}

env.go

@@ -46,6 +46,9 @@ func (e environment) keys() []string {
 	for key, _ := range e.items {
 		keys = append(keys, string(key))
 	}
+    if e.outer != nil {
+        keys = append(keys, e.outer.keys()...)
+    }
 	sort.Strings(keys)
 	return keys
 }

special.go

@@ -272,3 +272,12 @@ var begin = special{
 		return v, nil
 	},
 }
+
+var names = special{
+	name:     "names",
+	arity:    0,
+	variadic: false,
+	fn: func(env *environment, args []interface{}) (interface{}, error) {
+		return env.keys(), nil
+	},
+}