gistfile1.txt

{
  "ssl_certificate": {"$file": "/nginx/files/foobar"},
  "user": ["nobody", "nogroup"],
  "events": {
    "worker_connections": 1024,
    "accept_mutex": "on"
  },
  "http": {
    "gzip_disable": "\"MSIE [1-6]\\.\"",
    "upstream": {
      "testservers": {
        "server": [
          "example1.com",
          "foobar.com:8080"
        ]
      },
      "appservers": {
        "zone": {"$value": "/nginx/foo/bar"},
        "server": {
          "appserv1.example.com": null,
          "appserv2.example.com:8080": {
            "weight": "5"
          },
          "192.0.2.1": {
            "max_fails": 3
          },
          "reserve1.example.com:8080": {
            "backup": true
          },
          "reserve2.example.com:8080": {
            "backup": true
          }
        }
      }
    },
    "server": [
      {
        "server_name": "foobar.com",
        "location": {
          "@app": [
            ["proxy_set_header", "X-Forwarded-For $proxy_add_x_forwarded_for"],
            ["proxy_set_header", "X-Forwarded-Proto $scheme"]
          ],
          "= /500.html": {
            "root": "/path/to/app/current/public"
          }
        } 
      },
      {
        "server_name": "_",
        "try_files": ["$uri/index.html", "$uri.html", "$uri", "@app"],
        "location": [
          ["@app", [
            ["proxy_set_header", "Host $http_host"],
            ["proxy_set_header", "X-Forwarded-For $proxy_add_x_forwarded_for"]
          ]],
          ["= /500.html", {
            "proxy_set_header": {
              "X-Forwarded-For": "$proxy_add_x_forwarded_for",
              "X-Forwarded-Proto": "$scheme"
            },
            "root": "/path/to/app/current/public"
          }]
        ]
      }
    ]
  }
}

gistfile2.txt

ssl_certificate /path/to/file;
user nobody nogroup;
events {
	worker_connections 1024;
	accept_mutex on;
}
http {
	gzip_disable "MSIE [1-6]\.";
	upstream testservers {
		server example1.com;
		server foobar.com:8080;
	}
	upstream appservers {
		zone VALUE:/nginx/foo/bar;
		server appserv1.example.com;
		server appserv2.example.com:8080 weight=5;
		server 192.0.2.1 max_fails=3;
		server reserve1.example.com:8080 backup;
		server reserve2.example.com:8080 backup;
	}
	server {
		server_name foobar.com;
		location @app {
			proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
			proxy_set_header X-Forwarded-Proto $scheme;
		}
		location = /500.html {
			root /path/to/app/current/public;
		}
	}
	server {
		server_name _;
		try_files $uri/index.html $uri.html $uri @app;
		location @app {
			proxy_set_header Host $http_host;
			proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
		}
		location = /500.html {
			proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
			proxy_set_header X-Forwarded-Proto $scheme;
			root /path/to/app/current/public;
		}
	}
}