The thing to remember is that Pod parsers don't execute code. Pod and Perl are just two languages that can live in the same file and each parser just ignores the other language. So you can't use Perl constructs or source filters to affect how Pod parsers see the file.

However, you might be able to take advantage of the fact that perldoc will prefer a .pod file to a .pm file. For an example of how that could work, consider Pod::WikiDoc.

Pod::WikiDoc parses a .pm file containing "wikidoc" Pod format blocks when the distribution tarball is created and creates a matching .pod file with the wikidoc blocks converted to Pod. On installation, the .pod are what perldoc finds and end-users never need to know or care that I used Pod::WikiDoc to write my Pod.

You could do something similar where some template Pod format block gets expanded into a separate .pod file. You just need to customize a Pod parser to pre-process the .pm file, process your templates, and stick the results into a .pod file.