one of the documented procedures in this installation of the ACS
util_memoize_value_cached_p   tcl_statement   { oldest_acceptable_value_in_seconds "" }
What it does:
Returns 1 if there is a cached value for this Tcl expression. If a second argument is supplied, only returns 1 if the cached value isn't too old.
Defined in: /web/philip/packages/acs-core/utilities-procs.tcl

Source code:

    # we look up the statement in the cache to see if it has already
    # been eval'd.  The statement itself is the key

    if { ![nsv_exists util_memoize_cache_value $tcl_statement] || ( ![empty_string_p $oldest_acceptable_value_in_seconds] && ([expr [nsv_get util_memoize_cache_timestamp $tcl_statement] + $oldest_acceptable_value_in_seconds] < [ns_time]) )} {
	return 0
    } else {
	return 1