I would like to control which fields are displayed to the user upon display of the success_page.

This is a problem that templates are ideally suited to handle. Using HTML::Template, for example, a template to handle static {name, value} pairs might look something like

  <TMPL_IF foo>foo: <TMPL_VAR foo ESCAPE=HTML><br /></TMPL_IF>
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It's only slightly more complicated to handle dynamic {name, value} pairs.

  <TMPL_LOOP vars>
    <TMPL_IF value><TMPL_VAR name ESCAPE=HTML>:
      <TMPL_VAR value ESCAPE=HTML><br /></TMPL_VAR>
  </TMPL_LOOP>
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A Super Search for "HTML::Template" will turn up lots of examples to show how to set this up in code.