I was going to try different things, but a file being printed by the code you provided downloaded at 280KBs!!! (That's 1MB in 3.6 seconds!) I don't want to get into trouble with my employer or my web host, so I'm not going to do further testing.

Things I was going to try:

1. Unbuffered (sysread and syswrite instead of read and print).
2. Autoflushed STDOUT.
3. Using the NPH feature of CGI.
4. Combination of 1 and 3.
5. Combination of 2 and 3.

Actual code used:

#!/usr/bin/perl

use strict;
use warnings;

print("Content-Type: application/x-octect-stream\n");
print("\n");

use IO::File ();

my $data = IO::File->new('< file')
or die("Can't open data file: $!$/");

binmode($data);

my $block = '';
while ($data->read($block, 1024)) {
   print $block;
}
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