my @index = sort {
    $last[$a] cmp $last[$b]
    or
    $first[$a] cmp $first[$b]
} 0 .. $#first;

	 sort on multiple keys
Adler, Rich
Jackson, Jon
Jones, Fred
Jones, John
Smith, Joe
Smith, John

 	 But, testing, single sort (cmp):
	 Fred
	 Joe
	 John
	 John
	 Jon
	 Rich