do not take the question mark into query string

I have a redirect match rule which will convert part of the url into one query string which named _path, below is the configuration code:

addrule{ -- URI remapping example
  match = "^/core/(.+)",
  with = redirecthandler,
  params = {"/index.lua?&_path=%1"}
}

The origin redirect handler will take the ? into the query string.