my @sorted = sort @unsorted;

##</code><code>##

my @sorted = sort { $b cmp $a } @unsorted;

##</code><code>##

my $nextitem;
while ($nextitem = pop @rocks) {
    # Use $nextitem
}

##</code><code>##

for (my $i=1; $i <= @rocks; $i++) {
    my $nextitem = $rocks[- $i];    # Take the ${i}th item from the end
}