ESI
- beresp.do_esi — Whether to enable ESI on the fetched object
- esi.allow_inside_cdata — Whether to enable ESI directives inside CDATA blocks
- req.esi — Whether to enable ESI processing during a request
- req.esi_level — Level of ESI subrequest
- req.is_esi_subreq — Whether VCL is being evaluated within an ESI fragment
- req.topurl — For an ESI-generated request, the URL of the original request
