[judofyr]

There's a demo here: http://www.cliws.com/p/rjson/

It comes it to:

    {
      "users": [
        {
          "first": "Homer",
          "last": "Simpson"
        },
        [
          2,
          "Hank",
          "Hill"
        ],
        [
          0,
          2,
          "Peter",
          "Griffin"
        ]
      ]
    }