When the browser requests https://www.my-website.com/download.pl?file=path1/path2/filename.ext , you need to respond with the Content-Disposition header. Depending on what way you use to send headers, this might need different code. For Mojolicious, you send headers like the following:

use File::Basename 'basename';

...

# Serve static file if it exists
if (my $asset = $c->app->static->file('path1/path2/filename.ext')) {
    $c->res->headers->content_disposition('attachment; filename=filena
+me.ext');
    $c->reply->asset($asset);
}
[download]

Hi Corion. What is the $c variable? Please understand that I'm novice Perl programmer. Thanks, David

The $c variable is the context in Mojolicious. As you don't seem to be using Mojolicious, maybe you can tell us or even better show us the relevant parts of download.pl so we can better tell you how to add the header.

Please understand that I'm novice Perl programmer. Any help will be appreciated.

To take your novice Perl skills out of the equation, please take the time to read and understand the following non-Perl references:

• Minimal reproducible example (wikipedia)
• How to create a Minimal, Reproducible Example (SO)

If you're then convinced of the merit of at least attempting to create a minimal reproducible example, have a go at doing that in Perl (you might find Short, Self-Contained, Correct Example useful in this endeavour). If you get stuck, please feel free to ask for assistance, we will be glad to help.

Attempting to create a minimal reproducible example (even if unsuccessful) should have an added benefit of improving your general Perl skills and knowledge.

👁️🍾👍🦟

Since there's many ways to do things it's easier to help us to help you. Show what you've tried and how it failed, describe your situation. How do I post a question effectively?, tutorials -> PerlMonks for the Absolute Beginner.

Well, if you do not know the file type, assume MIME type "application/octet-stream". It's basically the same as saying to the User Agent (a browser in your case): "Here's some binary stuff of unspecified type".

use CGI;
my $html= new CGI;
#get the file name from URL ex. http://<server_IP>/cgi-bin/download.cg
+i?a=testing.txt
my $file= $html->param('a'); 
# $file is nothing but testing.txt
my $filepath= "/var/www/upload/$file";

print ("Content-Type:application/x-download\n");
print "Content-Disposition: attachment; filename=$file\n\n";

open FILE, "< $filepath" or die "can't open : $!";
binmode FILE;
local $/ = \10240;
while (<FILE>){
    print $_;
}

    close FILE;
 # use Unlink if u want to delete the files after download.
#unlink ($filepath);
[download]

Why do you call print with brackets then again without?

print ("Content-Type:application/x-download\n");
print "Content-Disposition: attachment; filename=$file\n\n";
[download]

Update: Looks like a copy/paste from SO https://stackoverflow.com/questions/15294815/perl-cgi-to-download-a-file-via-web-browser:

use CGI;
my $html= new CGI;
#get the file name from URL ex. http://<server_IP>/cgi-bin/download.cg
+i?a=testing.txt
my $file= $html->param('a'); 
# $file is nothing but testing.txt
my $filepath= "/var/www/upload/$file";

print ("Content-Type:application/x-download\n");
print "Content-Disposition: attachment; filename=$file\n\n";

open FILE, "< $filepath" or die "can't open : $!";
binmode FILE;
local $/ = \10240;
while (<FILE>){
    print $_;
}

    close FILE;
 # use Unlink if u want to delete the files after download.
#unlink ($filepath);
[download]

Ignoring the comment from davorg:

"Oops. I moved the articles around a bit. The link is not dead; it tells you where to go - perlhacks.com/articles/cgi-programming/cgi-programming-part-2. But to summarise, if I send you a file parameter of "../../../etc/passwd", you send me the file that contains all of your passwords for me to crack at my leisure. – Dave Cross Jan 19, 2017 at 5:56"

That worked great. Thanks so much, folks. I appreciate your efforts more than you can imagine.