I went into the CPAN shell and started with 'install Bundle::CPAN', which yielded the following errors:
Recursive dependency detected:
I found several other references to this problem, none of which provided a solution for me.
I traced the problem back to List::Util. One low-level module required version 1.21 (which was installed), but gave an error that version 1.19 was installed. I traced the problem to the fact that my Perl installation had two separate directories where List::Util was stored:
The first directory contained version 1.21, the second directory contained version 1.19.
I solved the problem by removing the multi-thread directories for List and for Scalar:
After this, I was able to install Bundle::CPAN.