switch to forEach to reduce for main return

 /***** Start *****/
 start
   = tags:lines+ .* {
-      var obj = {},
-          choices = {
+      var choices = {
         segments: 1,
         comments: 1,
         playlists: 1
       };
-      tags.forEach(function(tag) {
+      return tags.reduce(function(obj, tag) {
         for (var p in tag) {
           if (p in choices) {
             if (Object.prototype.toString.call(obj[p]) === '[object Array]') {
@@ -18,10 +17,11 @@ start
           } else {
             obj[p] = tag[p];
           }
-        }
-      });
+
           return obj;
         }
+      }, {});
+    }
 
 lines
   = comment:comment _ { var obj = {}; obj["comments"] = comment; return obj; }