Help needed with understanding Transclude widget & Fill

So, I decided I wanted to take a crack at recreating a plugin I use that makes a widget out of the details disclosure HTML elements, but unfortunately I think I am misunderstanding the instructions provided for the $fill portion of the $transclude widget.

I was under the impression the following would allow me to pass the $fill as the value for one of the parameters of the transclude widget.

If someone doesn’t mind explaining, how is it actually supposed to work…?

\define details(state:"open", summary:"placeholder", text, type:"h2")
<details $state$>
<summary><$type$ style="display:inline;">$summary$</$type$>
</summary><p>

$text$

</p></details>
\end

<$transclude 
$variable="details" 
summary="Hello There" 
$slot="text">

<$fill $name="ts-missing">
This content is displayed if `MissingTiddler` is missing.
</$fill>

<$fill $name="text">
hello There
<$/fill>

</$transclude>

just a quick update before going offline, I think I see where I went wrong in that i have to use the $slot widget to set what is filled using the $fill widget. still nit 100% sure how to pass the text parameter into the slot widget, but once im back online thatll be the first thing i try.