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 );
}