one of the documented procedures in this installation of the ACS
ad_context_bar   args
What it does:
Returns a Yahoo-style hierarchical navbar, each arg should be a list of URL and description. The last arg should be a just plain description.
Defined in: /web/philip/packages/acs-core/navigation-procs.tcl

Source code:

    set choices [list]
    set index 0
    foreach arg $args {
	incr index
	if { $index == [llength $args] } {
	    lappend choices $arg
	} else {
	    lappend choices "<a href=\"[lindex $arg 0]\">[lindex $arg 1]</a>"
    return [join $choices " : "]