fix template expression parse of regex and sequence (#2488)

fixes #2487

lib/parse.js

@@ -2107,7 +2107,8 @@ function parse($TEXT, options) {
         }));
         while (S.token.end === false) {
             next();
-            segments.push(expression());
+            handle_regexp();
+            segments.push(expression(true));
 
             if (!is_token("template_substitution")) {
                 unexpected();