sub quicksort_t {
    return @_ unless @_ > 1;
    my $pivot = shift;

    ## partition the data into 2 parts and run the standard recursive algorithm 
    ## on those two partitions in separate threads; return combined (joined) results
    my $t1 = asyncl sub{ quicksort( grep $_ <  $pivot, @_ ) }, @_;
    my $t2 = asyncl sub{ quicksort( grep $_ >= $pivot, @_ ) }, @_;
    return ( $t1->join, $pivot, $t2->join );
}