{
  "validator": [
    "Rx",
    {
      "schema": {
        "type": "//rec",
        "required": {
          "friend": {
            "type": "/perl/obj",
            "isa" : "TestFriend"
          }
        },
        "optional": {
          "how_long": "//any"
        }
      }
    }
  ],
  "header": [
    { "Subject": "Test Rx Message" },
    { "From":    "test@test.com"   }
  ],
  "type": "text/plain",
  "body": "This is a plaintext message."
}