0,2,,,10
0,2,,,15
0,1,,,984
0,2,,,9
1,14,,,5

2,34
1,984
14,5

awk -F, '{a[$2]+=$5};END{for(i in a)print i","a[i]}' <file

datamash -t ',' -s -g 2 sum 5 <infile

1,984
14,5
2,34

#!/usr/bin/env perl
use strict;
use warnings;

my %things;

while (<>) {
    my ( undef, $key, @rest ) = split(/,/);
    $things{$key} += pop(@rest);
}

foreach my $key ( sort { $a <=> $b } keys %things ) {
    print "$key = $things{$key}n";
}