DATA:
A,10
A,11
A,12
A,13
B,15
B,16
C,17
D,18

##</code><code>##

#!/usr/bin/perl

use strict;
use Data::Dumper;
open DATA,"read";
my %sum;
while (<DATA>) {
    next if ( /^ID/ || /^\s$/ );
    my ($id, $value) = split( "," );
    $sum{$id} = $sum{$id} + $value;
    
}

print Dumper \%sum;

##</code><code>##

output:
$VAR1 = {
          'A' => 46,
          'D' => '18',
          'C' => '17',
          'B' => 31
        };