[exim] Perhaps stupid Question regarding Filter

Hi Folks,

I have a small problem here. I currently have following rule in my
.forward:

if ($h_to matches "something@my_domain") and
      ($message_body contains "action:") and ($message_body contains
"DELETE") then
        save delete
      else
        save donotdelete

This causes on problem: I only want those mails with "action:" and
"DELETE" in ONE line to be saved do delete - but also mails like

[...]
action: some senseless action

You can delete files with rm
[...]

are saved to delete.

However, the problem is, that there may be one or more whitespaces
(Space, Tab) between "action:" and "DELETE".

And there may or may not be one or more whitespaces before or after
"DELETE".

Any ideas ?

Thanks and regards
Sascha