The Ape Base Compile System is a set of bash scripts to leverage both ESP EPM (http://www.epmhome.org/) and MREPO (http://dag.wieers.com/home-made/mrepo/) in maintaining Red Hat based systems that require custom and secluded binaries. If you need "Ape" to be an acronym, then go for "Application Packaging Environment" as christened by Mark Stokan. The original notion for the name was that this system was "aping" the performance of several tasks.
The most commonly useful of thes variables are already in the template "_blank_build_script-copy_to_create_your_own.sh" for use in creating your own scripts. There are several here that are not normally included in that template which may be useful to you for more complicated tasks. Processing a compile task begins as these variables are initialized where possible in "./include/ape_config.sh" and the settings in your coopy of "_blank_build_script-copy_to_create_your_own.sh" overwrites the values where needed. Finally, "./include/scripts_common.sh" performs any needed validation before starting the requested task.
The Ape Base Compile System internal system variables have yet to be documented for the end-user.