First I need to confirm that I really like the idea. Perl needs more publicity. Some may say that quality is more important than quantity but there is no better way to improve your writing skills than practice. So yeah - it's a great idea. In general I think we need more competitions - but that is really for another post.
There is just one small nitpick - if the goal is: "to promote the language to the world outside the Perl echo-chamber" then the rule that the all the posts need to be about Perl is misguided. If we want to talk to "the world outside the Perl echo-chamber" then we need to talk about the subjects that they care about. I can understand why we need some focusing - and posts about what you had for dinner are not the best way to promote the language - but it will be much easier to engage the outside audience if we wrote about general programming subjects. Look at advertisings - they don't talk about the advertised brand all the time, the more subtle the link is, the more engaging they are.
Update: I should have added that this post was inspired by Gabor Szabo: http://szabgab.com/blog/2009/06/1245788806.html