one of the documented procedures in this installation of the ACS
robot_p   useragent
What it does:
Returns true if the useragent is recognized as a search engine
Defined in: /web/philip/tcl/ad-robot-defs.tcl

Source code:

    ns_share ad_robot_useragent_cache

    # Memoize so we don't need to query the robots table for every single HTTP request.
    util_memoize ad_cache_robot_useragents

    if {[info exists ad_robot_useragent_cache($useragent)]} {
	return 1
    } else {
	return 0