one of the documented procedures in this installation of the ACS
ec_avs_acceptable_p   avs_code_from_cybercash
What it does:
Returns 1 if the AVS code is acceptable (implying that the consumer address sufficiently matches the creditor's records), or 0 otherwise
Defined in: /web/philip/tcl/ecommerce-credit.tcl

Source code:

    set acceptable_codes [list A W X Y Z]
    if { [lsearch $acceptable_codes $avs_code_from_cybercash] != -1 } {
	# code was valid
	return 1
    } else {
	return 0