That's easy to do. Just open up your JavaScript source file, and do a nice tight loop like so:

open (INPUT, $filename) or warn "Can't open $filename: $!";
print while (<INPUT>);
close INPUT;
[download]

You'll have to put that after the headers and in the appropriate spot of your HTML, but it's not tricky.

I think you can also refer to an external JavaScript source file within the HTML, but maybe I'm confusing it with CSS. That's probably even easier.