What you need is a template processing solution. I use Template::Toolkit myself. What you can do is:

<input type="text" name="foo" value="[% bar %]">
[download]

in you html. The html form is printed by the template processor (ie. Template::Toolkit or whatever), and all variables within the special tags (in this case [% %} are replaced.

I am sure that CGI.pm offers a solutions as well, but I don't use it for this so I don't know the syntax but you easy research that if you decide to go that way.