The same as 
%HTTP% but operates on the HTTPS environment variables present when the SSL protocol is in effect. Can be used to determine whether SSL is turned on. 
-  Called with the name of an HTTP request header field, returns its value. Capitalization and the use of hyphens versus underscores are not significant.
  -  Request headers are sent by the browser to the server. It is not possible to access the Response headers returned to the browser.
  -  Only returns headers permitted by site configuration.
  -  When called without a parameter, nothing is returned. See VarHTTPS for other options.
 
 

 The HTTP and HTTPS macros are deprecated as of Foswiki release 2.1. and will be removed in a future release.
 
  Parameters 
  Examples 
HTTP, 
REMOTE_ADDR, 
REMOTE_PORT, 
REMOTE_USER