sub Qsort  # WRONG! See update below!
{
    my $pivot = shift; # picking the pivot is usually more
                       # involved. Afterall, you don't want
                       # an extreme, you want both arrays to
                       # be roughly the same size.
    return $pivot unless @_;
    my( @lt, @gt );
    push( $_ gt $pivot ? @gt : @lt ) for @_;
    return( Qsort( @lt ), $pivot, Qsort( @gt ) );
}