Sadly I was too late for the discussion...
The following modification with loop in place of divide operation is almost as fast as the winner, i never thought that divide is so slow.

sub part {
    my ($n, $m) = @_;

    my $q = 0;

    $q++ while ($n-=$m) > 0;

    return ($q+1) x ($n+$m), ($q) x (-$n);
}
[download]