Hello KABA. Welcome to the Monastery!

The "Comments and Documentation" section at On Coding Standards and Code Reviews seems relevant to your comment, in particular:

• Separate user versus maintainer documentation.
• Include a comment block on every non-trivial method describing its purpose.

These are general guidelines, applicable to any language, not just Perl. Some prefer to comment Perl functions with POD. I find intermingling code with POD doesn't suit my brain, I prefer to put all the POD at the end of the file, and reserve it for public functions only (i.e. the external interface to the component) - I don't use POD to document internal functions.

When I describe a function parameter, I like to state explicitly whether it is an input parameter, an output parameter, or an "inout" parameter ("inout" parameters should be used sparingly).

Put another way, the POD at the end of the file is for the user of the module, the comment blocks at the top of each function are for the maintainer of the module (i.e. separate user versus maintainer documentation). The tricky bit is balancing this with DRY.