novice question

Hi,
here is a novice question. Is it possible to
make conditional use of INCLUDERC variable -
If yes how does one go about it?

I would like to use INCLUDERC=rc.abcxyz with
five different recipies if let us say 'abcxyz'
was present in head,

and use INCLUDERC=rc.thistext with another set
of recipies if 'thistext' was present in body
- and so on.

Thanks!
Niketan