How to get form values from successfully submitted form?

I'm using the Forms app and it's working well as usual. Now the client wants to use some of the form data in the success screen but I can't find a way to do this. <perch:showall /> doesn't show any form data whether or not show-form is true in the <success> tag. I even tried appending the form prefix, e.g. form1_name, with no luck. I was hoping a simple <perch:content id="name" type="hidden" /> would do it but it hasn't worked yet.

If using show-form="true" on the <success> tag the form appears on the success screen with the data populated, so I'm hoping there is some way of using that data in other ways in the <success> tag as well.

Thanks for your help!