@a = (['a',1],['a',2],['b',3],['b',4]); # "db read"

my $old;
my $total = 0;                          # init
foreach my $row (@a) {
        if ($old && $old ne $row->[0]) {
                print "$old: $total\n"; # finish row block

                $total = 0;             # init
                print "Section $row->[0]\n";
        }	

        $total += $row->[1];            # processrow block
        print "$row->[1]\n";        

        $old = $row->[0];               # set temp variable
}
print "$old: $total\n";                 # finish row block