What follows is data gotten from the HTTP request. It is all fully immutable, partially because it logically is (your code doesn't change what the user requested...) and partially because I hate how bad programs in PHP change those superglobals to do all kinds of hard to follow ugliness. I don't want that to ever happen in D.

For some of these, you'll want to refer to the http or cgi specs for more details.

class Cgi
immutable(string[string]) requestHeaders;