I've been in charge of code reviews at work for about six months now. A few random points:

• Before the code review, the code should be pushed through Perl::Tidy and Perl::Critic according to your internal coding standards. This avoids wasting time arguing about code layout and basic style issues. If you find things in a code review that were not detected by Perl::Critic, see if you can tweak your Perl::Critic policies to find them next time.
• The code review must be in writing. Otherwise, there is no proof it has been performed.
• Most of the code review work should be done before the code review meeting.
• Have at least two code reviewers.
• Take a look a Fagan Inspections. Though probably more formal than you want, you should get some good code review ideas from this well-respected method.

According to Karl Wiegers, the Seven Deadly Sins of Software Reviews are:

• Participants don't understand the review process.
• Reviewers critique the producer, not the product.
• Reviews are not planned.
• Review meetings drift into problem-solving.
• Reviewers are not prepared.
• The wrong people participate.
• Reviewers focus on style, not substance.

Some useful code review links:

• Seven Deadly Sins of Sotware Reviews article by Karl Wiegers.
• Peer Reviews in Software: A Practical Guide Addison-Wesley book by Karl Wiegers.
• Goodies for Peer Reviews.

Update: See also Re: I need perl coding standards (Coding Standards Links)