quicksort :: (Ord a) => [a] -> [a]  
    quicksort [] = []  
    quicksort (x:xs) =   
        let smallerSorted = quicksort [a | a <- xs, a <= x]  
            biggerSorted = quicksort [a | a <- xs, a > x]  
        in  smallerSorted ++ [x] ++ biggerSorted  

##</code><code>##

sub multi_thread_sort
{
    my @list = @_;
    
    my $pivot = shift @list;
    
    my @lowList  = grep { $_ <  $pivot } @list;
    my @highList = grep { $_ >= $pivot } @list;
    
    # Now start two threads to sort the two lists concurrently.
    
    return ( @lowList, $pivot, @highList );
}