f308c588_Apache_HTTP_Server_Version_2_4__Description
[Format] %l [Description] 
The current load averages of the actual server itself. It is designed to expose the values obtained by getloadavg() and this represents the current load average, the 5 minute average, and the 15 minute average. The value is preceded by l= with each average separated by /. Available in 2.4.4 and later.
mod_headers - Apache HTTP Server Version 2.4