[FormBuilder] Dynamic fields and templates

Hi,

I'm tying to build a form where most of the fields are standard fields, laid 
out via a template, but with a section where some fields may or may not be 
added dynamically, depending on the record type I'm editing.

The idea was that at run time I'd do something like:

my $tmpl = HTML::Template->new( ...)
$tmpl->param('form-start'  => "<tmpl_var form-start>"); 
$tmpl->param('form-submit' => "<tmpl_var form-submit>");
# all standard field template tags get replaced by themselves
# for FormBuilder to expand ...

$tmpl->param('dynamic-controls' => \@list_of_extra_fields);

# Now create the form object
my $form->CGI::FormBuilder->new( 
  fields =>\@list_of_all_fields,
  template => $tmpl,
   ....
);

This fails because $tmpl is an HTML::Template object and doesn't have a 
render() method.

Is subclassing CGI::FormBuilder::Template::HTML the only way to get something 
like this to work?   It seems odd that the template attribute can be an 
object reference but NOT an HTML::Template reference.
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