use strict;
use warnings;
use CGI qw(:standard);
use CGI::Carp qw(fatalToBrowser);

$|=1;

my $cgi = new CGI;

open FILE, "/whatever/the/path/to/file" or 
     die "Cannot open file for reading: $! ";
print $cgi->header("application/octet-stream");
print while(<FILE>);
close FILE;