use strict;
use warnings;

my %baldata;
while (defined(my $line = <DATA>)) {
    next unless $line =~ /^FB/;
    my ($key,$value) = split /\,/, $line;
    $baldata{$key} += $value;
}
foreach my $key (keys %baldata) {
    print "$key => $baldata{$key}\n"
}

__DATA__
ID,Value
FB208025,1629.01
FB208025,1201.16


FB091027,1257.66
FB091027,741.92

FB135022,11210.66
FB135022,3238.67
FB135022,3569.34
FB135022,5534.23