(I am original poster, damn cookies screwed up)
that is EXACTLY what I needed, and thanks for explaining it;
there was no REDIRECT_REQUEST_URI,
but there is a REDIRECT_URL as well as a
REQUEST_URI, both seem to be the same,
so I am happy using REDIRECT_URL.
(perl 5.6.1, apache 1.3.26, solaris 2.6, no mod_perl(?))