If you look at the source code of CGI, you can discover the code inside end_form that is adding all the extra hidden variables.

sub end_form {
    my($self,@p) = self_or_default(@_);
    if ( $NOSTICKY ) {
        return wantarray ? ("</form>") : "\n</form>";
    } else {
        if (my @fields = $self->get_fields) {
            return wantarray ? ("<div>",@fields,"</div>","</form>")
                             : "<div>".(join '',@fields)."</div>\n</fo
+rm>";
        } else {
            return "</form>";
        }
    }
}
[download]

As you can see above, the $NOSTICKY global will prevent the extra hidden fields that lead to the undesired default values. After reading the documentation of $NOSTICKY, you can set this in two different ways. One of them is more global:

use CGI qw(-nosticky);
[download]

Or you can is isolate the change to just the end_form function by doing the following:

print do {local $CGI::NOSTICKY = 1; $q->end_form()} . "\n";
[download]

Or you can just simplify the whole process for yourself by writing a simple </form> tag. Really don't know why someone wouldn't just do that anyway as the CGI module really does try to do too much in my opinion.