Answer.

POD is a built-in documentation format in Perl, historically appearing alongside the language's extension to support large projects. Its fundamental distinction is that documentation is always stored right in the source code, which helps maintain the connection between implementation and description (currently inseparable from the development of complex modules in Perl).

Problem: Often programmers either are not aware of or ignore automatic documentation generation systems, despite the fact that the Perl ecosystem (CPAN) clearly requires this for all modules.

Solution — use POD for every file, class, and function. There are automation tools like perldoc, pod2man, Pod::Coverage. A clear rule: if your module lacks POD, it will not be accepted in the corporate environment or will not be published on CPAN.

Code example:

=head1 NAME
My::Module - example of using POD

=head1 SYNOPSIS

  use My::Module;
  ...

=head1 DESCRIPTION

This function does...

=cut

Key features:

Simplicity of writing (readable by both humans and machines)
Integration with perldoc and CPAN
Many tools for generating documentation

Tricky questions.

Can POD be placed inside a subroutine and not just at the beginning of the file?

Answer: Yes, the POD specification allows insertions after any key constructions: after function declarations, methods, even within blocks.

What happens if you write code inside a POD block?

Answer: Everything between =pod (or another heading) and =cut is ignored by the interpreter. The code will not be executed! This is a common mistake.

How to document private functions in POD?

Answer: It is customary to add a section INTERNALS or PRIVATE FUNCTIONS, or not to include such documentation in SYNOPSIS. It is not recommended to completely hide documentation, especially if the library is public.

Common mistakes and anti-patterns

Leaving code inside POD — it doesn't work
Lack of description for exported functions
Documenting only the interface without usage examples

Real-life example

Negative case

The module is delivered without documentation. New developers have to read the source code, figuring out the magic parameters of the functions.

Pros:

Slightly less work at the initial stage

Cons:

Increased maintenance costs
Frequent bugs due to incorrect use of the interface

Positive case

All code is accompanied by POD, usage examples are provided in the SYNOPSIS section, each function is described, and limitations are noted.