use strict;
use warnings;
use Data::Dumper;

my @class = (40, 40, 40, 183, 183, 259, 244, 503);
my @qty = (260, 234, 211, 301, 401, 321, 210, 451);
my %bin =   ( 0 => [0,0],
             40 => [0, 0],
            183 => [0, 0],
            503 => [0, 0],
            442 => [0, 0],
            259 => [0, 0],
            244 => [0, 0]);
my ($i, $hkey);

for($i = 0; $i <= $#class; $i++) {
    $hkey = $class[$i];
    my $tmp_count = $bin{$hkey}[0]+1;
    my $tmp_sum = $bin{$hkey}[1]+ $qty[$i];
    $bin{$hkey}[0] = $tmp_count;
    $bin{$hkey}[1] = $tmp_sum;
#   $bin{$hkey}[0, 1] = [$tmp_count, $tmp_sum]; #why not?
}
print Dumper (%bin);

##</code><code>##

#   0 => [ 0,   0];
#  40 => [ 3, 705];
# 183 => [ 2, 702];
# 259 => [ 1, 401];
# 442 => [ 0,   0];
# 244 => [ 1, 321];
# 503 => [ 1, 210];