one of the documented procedures in this installation of the ACS
ad_generic_optionlist   items   values   { default "" }
What it does:
Use this to build select form fragments. Given a list of items and a list of values, will return the option tags with default highlighted as appropriate.
Defined in: /web/philip/packages/acs-core/widgets-procs.tcl

Source code:

    # items is a list of the items you would like the user to select from
    # values is a list of corresponding option values
    # default is the value of the item to be selected
    set count 0
    set return_string ""
    foreach value $values {
	if {  [string compare $default $value] == 0 } {
	    append return_string "<option SELECTED value=\"$value\">[lindex $items $count]\n"
	} else {
	    append return_string "<option value=\"$value\">[lindex $items $count]\n"
	incr count
    return $return_string