| Subject: | as of CPAN-2.10, cpan -J may no longer emit pure perl code |
according to the docs, cpan -J "dumps the configuration in the same format that CPAN.pm uses". but as of CPAN-2.10, if Log4Perl is not available (which is neither required nor recommended nor suggested), the output of cpan -J starts with a line "Loading internal null logger. Install Log::Log4perl for logging messages". so the output has to be sanitized before it is usable by a subsequent cpan -j.
github commit 6f971c4 seems the root of the problem: the commit introduces a line
print "Loading internal null logger. Install Log::Log4perl for logging messages\n";
to sub _init_logger() of lib/App/Cpan.pm.