Content-Type is a header, you get one per document, and I don't think that's what you want.

Depending on what print_binary_data does, you could just replace it with a series of 10 images, each showing a single digit, and then reading your counter file, as below.

use CGI qw(:standard);

my $lines=<DATA>;
chomp $lines;
while ($lines=~/(\d)/g) {
    print img{src=>"$1.gif"};
    print "\n";
}
__DATA__
5123496780
[download]