Is there a way, in POD, to accumulate POD comments in multiple files into one larger document? This way
there would truly be a single point of documentation.
There is no way in POD, but there are many ways in Perl
(at least, there is more than one way...) Go to
http://www.cpan.org/modules/01modules.index.html
and you will find more than 30 modules dealing with POD.
In your case, maybe Pod-Simple or Pod-Parser is what you
need.
With either module, extract the POD from each file and
copy it to the result file. That's simple.