Depending on the intended use of Perl itself the training got to be geared to lean more towards certain areas at the expense of others. Emphasis is that, Perl has a low entry point and many many application areas, learning it is not going to be a rough ride but then getting to write it the right way and adhering to the best practices or whatever coding consensus established at your organization is what is more important.

So, if you do more of data/text processing then touching on file/folder management, regular expressions, loops, I/O operations, buffering, different ways to open and read files, data structures and persistence so modules like DB_File, Storable..etc come to mind. If you are on the web programming side, CGI, Socket programming, IPC, DNS resolution are maybe what needs to go under the spotlight. If you are on the Graphical side, Tk and company

But notwithstanding, developing the way to think a situation through is worthwhile, I mean, you may not teach them everything but make them aware of the topics and resources that they can reach to and how they go about it, so perldoc, CPAN, The Monastery and references to interesting books need to be mentioned...