[...]
    # read one byte
    read($fh, $buffer, 1);

    if(defined($buffer)) {
        # get an unsigned char
        my $v = unpack("C", $buffer);

        # sum the squared distance from the theoretical mean
        $sse += ($v-127.5)**2;
        $cnt++;
    } else {
        print "No byte here\n";
    }
[...]