is this what you are looking for?

foreach $key (sort(keys %ENV)) {
   print "VARIABLE $key = $ENV{$key}\n";
}
[download]

Which will give you below, with associated values

DOCUMENT_ROOT  
HTTP_COOKIE    
HTTP_HOST      
HTTP_REFERER   
HTTP_USER_AGENT  
HTTPS     
PATH    
QUERY_STRING   
REMOTE_ADDR  
REMOTE_HOST 
REMOTE_PORT     
REMOTE_USER 
REQUEST_METHOD    
REQUEST URI   
SCRIPT_FILENAME  
SCRIPT_NAME      
SERVER_ADMIN      
SERVER_NAME     
SERVER_PORT      
SERVER_SOFTWARE

Did that answer your question?
update: ikegami has a nice one liner. Are you looking for that, more like mine or something else?