[O] Filtering in export hooks

[suvayu ali]

Hi Orgers,

What is the recommended way to filter/select headlines I want to
preprocess in any of the export hooks? I have tried using tags like
this:

(let ((match "tag1|tag2"))
  (org-map-entries (lambda () (my-preprocess-function))
                   match))

But this only works when tags: is non-nil. Any hints on how I could
achieve something that "works always"?

Thanks for any response.

-- 
Suvayu

Open source is the future. It sets us free.