use strict;
use warnings;

use CGI;
use HTML::Template;

my $q    = CGI->new;
my $tmpl = HTML::Template->new(
   filehandle => \*DATA,
   associate  => $q,
);

print $q->header, $q->start_html;

if ($q->param('cmd') eq 'confirm') {
   print $q->p("the user confirmed");
}
else {
   print $tmpl->output;
}

__DATA__
<tmpl_if cmd>
   You submitted:
   <ol>
      <li>foo: <tmpl_var foo></li>
      <li>bar: <tmpl_var bar></li>
   </ol>
   You like?
   <form>
   <input type="hidden" name="cmd" value="confirm" />
   <input type="submit" value="yes" />
   </form>
<tmpl_else>
   <form>
   foo: <input type="text" name="foo" /><br/>
   bar: <input type="text" name="bar" /><br/>
   <input type="hidden" name="cmd" value="ask" />
   <input type="submit" />
   </form>
</tmpl_if>