You could investigate using cookies instead of hidden form fields.

Cookies are quite simple w/ CGI.pm. To set a cookie:

use CGI;
my $query = new CGI;
my $cookie = $query->cookie(-name  => 'id',
                            -value => 'foo');
print $query->header(-cookie => $cookie);
[download]

To retrieve a cookie:

use CGI;
my $query = new CGI;
my $id = $query->cookie(-name => 'id');
[download]

There are other parameters you can set for a cookie--read the CGI.pm docs to find out about them.