use strict;
use warnings;
use feature 'say';

my %hash;
while (<DATA>) {
    chomp;
    my ($id, $num, $val) = split /,/, $_;
    $hash{"$id,$num"} += $val;  
}

for my $key (sort keys %hash) {
    say "$key,$hash{$key}"; 
}

__DATA__
3211111,100,3.2
3211112,101,3.2
3211111,100,1.2
3211112,100,2.2
3211113,100,5.2
3211112,100,0.3