!!! Overview
[{$pagename}] are used in some [HTTP Header Fields]

But I can not find a formal registry or source for the [{$pagename}]s definitions.

For example the "[Cache-Control]" [HTTP Cache Directives] is used to specify __directives__ for caches along the request/response chain.

!! More Information
There might be more information for this subject on one of the following:
[{ReferringPagesPlugin before='*' after='\n' }]