OK, I solved it. What needed to be done was, to clear the CPANPLUS cache (whatever that is), by entering "x" at the cpanp prompt. Apparently cpanp keeps a cache somewhere (and I don't think it's under the
C:\Documents and Settings\UserName\.cpanplus\
tree), and that cache contains configuration parameters, including the current (=default) Perl installation top directory.

Also, after extensive googling, quite far away in a search result list, I have found this:

How can I use CPANPLUS with multiple versions of Perl?
You only need one installation of CPANPLUS for all versions of Perl. As of version 0.04, CPANPLUS keeps different directories under its home directory for each version of Perl:
    .cpanplus/
        authors/
            id/     # tarballs live here
        5.6.0/
            build/
        5.7.3/
            build/

[download]

This prevents conflicts.

(URL: http://cpanplus.sourceforge.net/faq.html#b)

So, conclusions:

  1. Installing several Perl versions is ok and supported
  2. CAPNPLUS supports working in a multi-perl installation environment, but you must clear the "CPANPLUS cache" when shifting from one installation to the other (or use some other alternatives listed in that URL)
  3. CPANPLUS documentation is meager and practically non-existent. I found the URL quoted above by accident, and its parent URL is broken.

That has been an excruciating experience. I have spent days wrestling with this.

Many thanks to all PerlMonks trying to help, offering advice - Helen

In reply to Re^6: The CPANPLUS cache had to be cleared by HelenCr
in thread cpanplus not functioning right in a multiple-Perl installation setup? by HelenCr

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