anchor.diff:                       "Organization: Boxes by Bob\r\nPriority: non-urgent\r\n",
                        "Proxy-Authenticate: Digest realm=\"atlanta.com\"\r\nProxy-Authorization: Digest username=\"Alice\"\r\n",
                        "Proxy-Require: foo\r\nRecord-Route: <sip:server10.biloxi.com;lr>\r\n",
  -                     "Reply-To: Bob <sip:bob@biloxi.com>\r\n"
  +                     "Reply-To: Bob <sip:bob@biloxi.com>\r\nRequire: foo\r\n",
   
                        "Content-Length: 5\r\nVia: SIP/2.0/UDP localhost\r\n",
                        "To: sip:bob@localhost\r\n"
                        "x-custom-atom: 25\r\nAllow: INVITE, ACK, CANCEL, OPTIONS, BYE\r\n",
  -                     "Supported: 100rel\r\nUnsupported: bar, baz\r\nRequire: foo\r\nProxy-Require: some\r\n",
  +                     "Supported: 100rel\r\nUnsupported: bar, baz\r\n",
                        "X-Custom: value\r\n">>,
                      format_headers([{'accept', <<"*/*">>}, {'accept-encoding', <<"identity">>},
                                      {'accept-language', <<"en">>}, {'alert-info', <<"<http://www.example.com/sounds/moo.wav>">>},
  
positive.code:                                    {'x-custom-atom', 25},
                                     {'allow', <<"INVITE, ACK, CANCEL, OPTIONS, BYE">>},
                                     {'supported', <<"100rel">>}, {'unsupported', <<"bar, baz">>},
                                     {'require', <<"foo">>}, {'proxy-require', <<"some">>},
                                     {<<"X-Custom">>, <<"value">>}])),
  
       % Already parsed
  
negative.code:                                    {'organization', <<"Boxes by Bob">>}, {'priority', <<"non-urgent">>},
                                     {'proxy-authenticate', <<"Digest realm=\"atlanta.com\"">>}, {'proxy-authorization', <<"Digest username=\"Alice\"">>},
                                     {'proxy-require', <<"foo">>}, {'record-route', <<"<sip:server10.biloxi.com;lr>">>},
                                     {'reply-to', <<"Bob <sip:bob@biloxi.com>">>}, {'require', <<"foo">>},
  
  
                                     {'content-length', <<"5">>}, {'via', <<"SIP/2.0/UDP localhost">>},
  