CONTENT_LENGTH -- taken directly from request
CONTENT_TYPE -- taken directly from request
GATEWAY_INTERFACE -- "CGI/1.1"
PATH_INFO -- <path> component of URI

QUERY_STRING -- parsed from URI as everything after ?:

        However, a subset of URI do share a common syntax for
        representing hierarchical relationships within the namespace.  This
        "generic URI" syntax consists of a sequence of four main components:

                <scheme>://<authority><path>?<query>

        each of which, except <scheme>, may be absent from a particular URI.
        For example, some URI schemes do not allow an <authority> component,
        and others do not use a <query> component.

Example: /cgi/testfun/arg1/arg2/arg3?test=test

    --> PATH_INFO = /testfun/arg1/arg2/arg3 [trailing slashes matter]
    --> REQUEST_URI = /cgi/testfun/arg1/arg2/arg3
    --> QUERY_STRING = test=test
    --> SCRIPT_NAME = /cgi [hard-coded] 

REMOTE_ADDR -- taken when accept() call is made
REQUEST_METHOD -- taken directly from request
REQUEST_URI -- taken directly from request
SCRIPT_NAME -- hard-coded/configured application name (virtual path) 
SERVER_PORT -- as configured from command line (HTTP or HTTPS port depending)
SERVER_PROTOCOL -- "HTTP/1.1"
SERVER_SOFTWARE -- "Liso/1.0"
HTTP_ACCEPT -- taken directly from request
HTTP_REFERER -- taken directly from request
HTTP_ACCEPT_ENCODING -- taken directly from request
HTTP_ACCEPT_LANGUAGE -- taken directly from request
HTTP_ACCEPT_CHARSET -- taken directly from request
HTTP_HOST -- taken directly from request
HTTP_COOKIE -- taken directly from request
HTTP_USER_AGENT -- taken directly from request
HTTP_CONNECTION -- taken directly from request
HTTP_HOST -- taken directly from request