protecting internal redirects

Hi all,

This is not exactly a mod_perl question - in fact I hope there is a
solution which does not use mod_perl.

I have a CGI script which generates a lot of output. Because it takes
a lot of time to the output, the results are cached in case the same
request is made again.

To serve the file the CGI script issues an internal redirect to a url
which points to the cached results.

My question is: can the url which points to the cached results be
protected so that it cannot be directly accessed by external clients?

For example:

1. user makes a request
2. CGI script handles request. It computes a file name for the
results, generates the results and places the result in that file.
3. The CGI script then emits an internal redirect to a url which will
map to the file name determined in step 2.
4. Apache will process the internal redirect and serve the contents of
the file to the client.

I want to prevent the clients from accessing the file directly by
figuring out what the url is in step 3.
I know that clients will not see the internal redirect, but I also
want to prevent them from guessing it.

Is there an Apache configuration I can use to accomplish this, or do I
need to use mod_perl?

Thanks,
ER