sub my_sort_index {
    my ($c, $d) = @_;
    # We want any item starting with "index." to sort to the top of
    # the list.  The rest of the ordering is handled by the caller.
    # So there are four cases we must handle:
    #
    #   Matches?
    #   $c    $d   return
    #   No    No     0 
    #   Yes   No    -1
    #   No    Yes   +1
    #   Yes   Yes    0     (-1 + +1 == 0)
    #
    # In the fourth case, when both strings have the "index." prefix,
    # we want them to sort via the normal method so that "index.1" will
    # always sort before "index.2".

    my $return_value = 0;
    --$return_value  if $c =~ /^index\./;
    ++$return_value  if $d =~ /^index\./;
    return $return_value;
}