sub range_to_list {
    my( $max, $range ) = @_;
    my( $lo, $sep, $hi ) = $range =~ m[^(\d+)?(?:(-)(\d*))?$] or die "Invalid range:$range\n";
    $lo ||= 0; 
    $hi ||= $sep ? $max : $lo;
    $_ > $max and die "$_ out of range\n" for $lo, $hi;
    return $lo .. $hi;
}