After seeing this in Rack::Utils (my IDE even highlighted it because it’s the only one in double quotes):
HTTP_STATUS_CODES = { 100 => 'Continue', 101 => 'Switching Protocols', ... 418 => "I'm a Teapot", ... }
I had to look it up: http://tools.ietf.org/html/rfc2324
Thanks to laserlemon I can finally implement my fully web-controlled coffee pot with Sinatra on Rack!