I used a lot of perseverance and I knocked many doors and after some initial misunderstandings, I was given attention in the #toolchain irc perl channel (thanks Tux to address me there).

Some smart guys lurk there and they finally been able to reproduce my errors (the use of initialized value in File::Spec::Win32 just after the start of configuration o conf init test_report inside cpan client). This will happen only with portable strawberry edition and not with the installed version (.msi package), but seems to happen with every portable version.

A good advice I got was: set PERL5OPT=-d:Confess which highligthed a bit more the error source:

Use of uninitialized value $_[0] in string eq at D:/SCRIPTS/perl5.26-6
+4bit/perl/lib/File/Spec/Win32.pm line 157.
        File::Spec::Win32::catdir("File::Spec", undef, ".cpanreporter"
+) called at D:\SCRIPTS\perl5.26-64bit\perl\site\lib/CPAN/Reporter/Con
+fig.pm line 362
[download]

which lead to File::Homedir asking for my_documents

# installed straberry perl
perl -MFile::HomeDir -E "say +File::HomeDir->my_documents(); say $File
+::HomeDir::IMPLEMENTED_BY"

C:\Users\NAME\Document
File::HomeDir::Windows

# portable straberry perl
perl -MFile::HomeDir -E "say +File::HomeDir->my_documents(); say $File
+::HomeDir::IMPLEMENTED_BY"

                        # <--- NO OUTPUT aka undef!
Portable::HomeDir
[download]

Infact the portable versions have a portable.perl which defines

HomeDir:
   my_home: data
   my_data: data
[download]

But not my_document tadà! The minimal effort patch was already submitted at strawberry github repository

So we are going in the right direction, even if many things are still pending:

1- if the above patch will be accepted then portable editions will correctly use data/.cpanreporter (without warnings) ( update March 18th 2019 the PR was merged)

2- installed aka non portable SP were not affected by the above

3- as side note Data::UUID has a pending PR to use File::Spec->tmpdir instead of c:\tmp ( PS see Data-UUID/pull/32 ) update March 2019 PR has gone into new release

4- setting PERL_CPAN_REPORTER_DIR to something valid would avoided the above errors

5- documentation at cpan tester quick start guide needs to be reviewed a bit

PS oh I missed some important stuff!

Given the above PERL_CPAN_REPORTER_DIR seems to be the clues to have the single or smoke env to be setu correctly. A system wide env set or a replicated var for each portable installation (I prefere the latter..) will be the trick (to be still tested).

Another good news is that there is a mailing list (low traffic) and I signed to it. A message has a lot of useful informations: see it archived

L*