Perhaps a better question would be, "What can a high level on Perlmonks demonstrate?"
In my case, it's on my CV for several reasons. First, to show that I've participated in a fairly successful technical forum for a year and a half. Second, to show that I'm a fairly-well respected contributor. Third, as an example of some of my programming, and my progress over the past months.
That's not a substitute for providing example code or a guarantee for how I might work with a team, but it looks pretty good in a biography. ("Hey, this guy's reviewed several programming books and is a high-level poster at a programming site. Maybe he has something worth saying.")