I have tab delimited data with multiple columns.

I have OS names in column 31 and data bytes in columns 6 and 7. What I want to do is count the total volume of each unique OS.

So, I did something in Perl like this:

#!/usr/bin/perl
use warnings;

my @hhfilelist  = glob "*.txt";
my %count = ();

for my $f (@hhfilelist) {
    open F, $f || die "Cannot open $f: $!";
    while (<F>) {
        chomp;
        my @line = split /\t/;
        # counting volumes in col 6 and 7 for 31
        $count{$line[30]} = $line[5] + $line[6];     
    }
    close (F);
}

my $w = 0;

foreach $w (sort keys %count) {
    print "$w\t$count{$w}\n";
}

So, the result would be something like

Windows    100000
Linux        5000
Mac OSX     15000
Android      2000

But there seems to be some error in this code because the resulting values I get aren't as expected.

What am I doing wrong?