| DOCUMENT_ROOT | $ENV{DOCUMENT_ROOT} | The root directory of your server |
| HTTP_COOKIE | $ENV{HTTP_COOKIE} | The visitor's cookie, if one is set |
| HTTP_HOST | $ENV{HTTP_HOST} | The hostname of the page being attempted |
| HTTP_REFERER | $ENV{HTTP_REFERER} | The URL of the page that called your program |
| HTTP_USER_AGENT | $ENV{HTTP_USER_AGENT} | The browser type of the visitor |
| HTTPS | $ENV{HTTPS} | "on" if the program is being called through a secure server |
| PATH | $ENV{PATH} | The system path your server is running under |
| QUERY_STRING | $ENV{QUERY_STRING} | The query string (see GET, below) |
| REMOTE_ADDR | $ENV{REMOTE_ADDR} | The IP address of the visitor |
| REMOTE_HOST | $ENV{REMOTE_HOST} | The hostname of the visitor (if your server has reverse-name-lookups on; otherwise this is the IP address again) |
| REMOTE_PORT | $ENV{REMOTE_PORT} | The port the visitor is connected to on the web server |
| REMOTE_USER | $ENV{REMOTE_USER} | The visitor's username (for .htaccess-protected pages) |
| REQUEST_METHOD | $ENV{REQUEST_METHOD} | GET or POST |
| REQUEST_URI | $ENV{REQUEST_URI} | The interpreted pathname of the requested document or CGI (relative to the document root) |
| SCRIPT_FILENAME | $ENV{SCRIPT_FILENAME} | The full pathname of the current CGI |
| SCRIPT_NAME | $ENV{SCRIPT_NAME} | The interpreted pathname of the current CGI (relative to the document root) |
| SERVER_ADMIN | $ENV{SERVER_ADMIN} | The email address for your server's webmaster |
| SERVER_NAME | $ENV{SERVER_NAME} | Your server's fully qualified domain name (e.g. www.cgi101.com) |
| SERVER_PORT | $ENV{SERVER_PORT} | The port number your server is listening on |
| SERVER_SOFTWARE | $ENV{SERVER_SOFTWARE} | The server software you're using (e.g. Apache 1.3) |