Most servers, with the default setup, won't let you put a perl script into an HTML page with the extension ".html" -- you can use ".shtml" instead, or you can change the server settings so that ".html" is "server-parsed".

Once you've got either of those sorted out, you can use a special include tag:

<!--#exec cgi="/path/to/script"-->
[download]

or possibly just

<!--#include virtual="/path/to/script"-->
[download]

but by the time you've gone to all that trouble, why not just create your whole page with Perl? If you don't have an "index.html" your server will probably look for "index.cgi" and display that instead.