"You should always declare in your Makefile.PL (or Build.PL, or other build instructions) *all* the modules your code depends on. That's because older versions of perl have fewer modules in core"

I agree, but the modules in question have been core since 5/5.6.

"I presume that that is a list of all the modules used by the code"

Is it? Perhaps. Khen1950fx has a history of posts like this where there's no difference from doing cpan Module::Name, also forcing installs so potential problems are missed and even going so far as to create a module on cpan (infact I just found another, Task::Mechanistic, again pointless) to install another module. None of this makes any sense from a module installation perspecitve.

Update: s/installing/install/