So I reported a problem to an author, and even diagnosed it for him cos I'm such a nice guy, saying that "In the pre-requisites you list the 'B' and 'O' modules. But those don't exist seperately on the CPAN, only as part of perl itself, so don't need to be listed. In fact, listing them can confuse some build tools and if the user has a very old version of CPAN.pm it might even try to build a new perl for them."
He replied "Well, honestly I think that you need to improve those build tools; or otherwise cite some docs saying that it is illegal to list the modules in PREREQ_PM which are part of perl."
I wonder which part of "a very old version of CPAN.pm" - that is, it doesn't apply to the current version - he is too stupid to understand, and why he thinks that other peoples' bugs are my problem.