Anonymous Monk gets two upvotes.

In code I have seen, you find, say:   [%WRAPPER wrap/dialog.tt mode="popup"%].

Then, within that wrapper file:

[%IF mode == "popup" %]
  ... directives for a popup ...
[% ELSE %]
  ... directives for anything else (i.e. "mode" not specified) ...
[% END %]
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