my $a = 5;

my @b = reverse (0 .. 9);
print "@b\n";

sub boo {
$a <=> $b
}

@b = sort boo @b;
print "@b\n";
print $a,$/;
----
9 8 7 6 5 4 3 2 1 0
0 1 2 3 4 9 8 5 6 7
5