my @a = split/:/,$str;
@a % 2 && die;                # not an even number of items
my $r = int(rand(100));
my ($adId, $p);
while (($p,$adId) = splice @a,0,2) {
   if ($r < $p) {last;}
   $r -= $p;
}


##</code><code>##

            Rate origCode     duff       QM      L~R      ccn   fizbin
origCode  4029/s       --     -34%     -77%     -82%     -87%     -89%
duff      6137/s      52%       --     -65%     -73%     -81%     -83%
QM       17360/s     331%     183%       --     -24%     -46%     -53%
L~R      22908/s     469%     273%      32%       --     -29%     -38%
ccn      32106/s     697%     423%      85%      40%       --     -12%
fizbin   36690/s     811%     498%     111%      60%      14%       --


##</code><code>##

--
@/=map{[/./g]}qw/.h_nJ Xapou cets krht ele_ r_ra/;
map{y/X_/\n /;print}map{pop@$_}@/for@/