The module system linked to file structure worked for Perl pretty well. Perl had this crazy idea that different authors should publish packages/modules with the same namespace, e.g.

  IO.pm                      <-- author: Larry Wall
  IO/File.pm                 <-- author: Me
  IO/Socket.pm               <-- author: You
  IO/Socket/INET.pm          <-- author: Larry Wall
  IO/Socket/INET/Daemon.pm   <-- author: Me

Simpler and encourages code reuse. Of course there is duplicate code in CPAN, but you really have to go out of your way to avoid an existing module that can do what you need.