How can I use pa_macro to substitute in a constant into a program?

A real example:

Makefile ------------------------------------------------------------

PACKAGE = foo
VERSION = 1.0.0

version.cmo: version.ml Makefile
	ocamlc -I +camlp4 -pp 'camlp4o pa_macro.cmo -DPACKAGE="$(PACKAGE)" -DVERSION="$(VERSION)"' $< -o $@

version.ml ----------------------------------------------------------

let package = PACKAGE
let version = VERSION

---------------------------------------------------------------------

Needless to say this example doesn't work, and looking at the thin
documentation for pa_macro, I'm not even sure it's possible.  Is it?

Rich.

-- 
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