I've acutally been through this a couple of times, and I'm currently training a friend. I recommend finding something your intern knows how to do from the command line and set them to automating it. One advantage to this approach is that they already know how it should work, so they can focus on the programming aspect.

For example, have them write a log file filter. Set them to writing a script that will open a logfile, search for key data, and output that data to a separate file.

Another task would be to have them write a wrapper around ping, host, and traceroute that would crawl your network. The output might actually be useful, as you may discover some things about your network.

Another good project is a tool that uses MP3::Tag to manipulate the tags on an mp3 collection. It's a good project for learning perl modules, hashes, and pattern matching.

Finally, as to the Camel and Llama books, if your intern wants to code perl, they need the Camel book. It's a formal requirement. Period. If they're so dead broke that they can't afford used copies (and I remember those days), and your company refuses to pony up for a corporate copy of O'Reilly's CD bookshelf, and you can't get them to trade for it ("Mow my lawn and wash my car and I'll buy you the damn book, kid"), there's a solution. It's not pretty, and it's illegal I'm sure: Google for it.