you could always have a button that would go to a function and basically submit the form if the user clicked ok on the confirmation message. i.e.

<input type="button" name="submit" value="javascript: submitForm();">

<script language="javascript">
  function submitForm() {
    if (confirm("delete account?")) {
      mainForm.submit();
    }
   }
</script>
[download]

this wasn't a very perl-y example.. but it's similar to what simon.proctor suggested.