You could use this env vars:

** Protocol
HTTP       = "0.9" "1.0" "1.1".
METHOD     = Usually GET,PUT,POST,OPTIONS...
FILE       - File to acces.
ORIG_FILE  - An original copy of $FILE.
DIR        - Directory where's the file requested by METHOD.
FILETYPE   - Extension of file (html,gif,jpeg...).
HTTP_LIMIT = "TRUE" || "" - Did server arrive at http limits?.
HOST       - Host (if defined) useful to create virual-hosts. (Deprecated)
USERAGENT  - (if defined) User-Agent of the client.
REFERER    - (if defined) Referer of the client (the last page visited).
CONNECTION - Closed, Keep-Alive. or wathever user says
CONTENT    - The content posted by the user
CLENGTH    - Content-Length (Useful to test if is really POST)
CODE       - Code returned by the page only after exec (200,404..)
RANGE      - range string
RANGE_LEN  - length of range requested by user
RANGE_SEEK - Offset position from the beggining of the file.

** Arguments
ARGS_ENABLES - "TRUE" || ""
ARGS - Argument string
ARGC - Number of arguments
ARGV - A space-separated arguments env
ARG_VARNAME - Every VARNAME is accessed in this method.

** Connection
LISTEN_PORT - Port where server listens
LISTEN_ADDR - Address where server listens
LISTEN_HOST - Clone of deprecated 'HOST' var.
REMOTE_PORT - Remote port
REMOTE_ADDR - Remote address
REMOTE_HOST - Remote hostname
FAMILY      - Protocol family (4||6)
TCPWINSIZE  - SO_SNDBUF value of the socket.

** Server
DATE      - Date string to be print on headers
VERSION   - Server version
IPV6      - "TRUE" || "" - compiled with ipv6 support
POLL      - "TRUE" || "" - compiled with poll support
LOGS      - "TRUE" || "" - compiled with logs support
THREAD_ID - Returns the thread identification defined in the configuration file
IO        - POLL|BUFFER|DIRECT|SELECT

** System Related
HOSTNAME  - Current hostname
UNAME     - Uname output string
SYSNAME   - OS Name
SYSVERSION- OS Version string
RELEASE   - OS Release version
MACHINE   - Architecture
