There are multiple ways you can tackle this

1. Sessions
2. Cookies
3. Hidden inputs

Try something like this:

if ($q->param('submit1') eq 'submit1') {
    $index="Some val";
    print "DEBUG after 1st submit " . $index . "<br>";
    print $q->hidden('index', $index);
    print $q->submit(-name=>"submit2",
         -label=>"submit2") . " ",
}
[download]

Later in the script, you can then 'recover' the value with $q->param('index')