For clarification, depending on the paths in the ENV perldoc might "find" different documents to generate doc.

This is particular relevant if there is a NAME.pod file, forcing perldoc to ignore NAME.pl or NAME.pm.

-l is supposed to show the path of the original files.

In the case of -f both perlfunc and perlop must be "found" (and parsed) and -l will show their paths.

This is actually relevant for debugging a messed up environment with multiple Perl installations.

Edit

According to perldoc the paths in PERL5LIB and PATH are searched for matching files.