my $binSize = 20;
my $bin = 0;
my $total = 0;

while ((my $line = <DATA> // '') || defined $bin){
    chomp $line;
    my ($chr, $pos, $coverage) = split /\t/, $line;
    my $thisBin;

    $thisBin = int(($pos - 1) / $binSize) if defined $pos;

    if (! defined $thisBin || $bin != $thisBin) {
        printf "%4d %d\n", 20 * (1 + $bin), $total;
        last if ! defined $thisBin;

        $bin = $thisBin;
        $total = 0;
    }
    
    $total += $coverage;
}