Over a year ago I wrote a Perforce implementation for CruiseControl.rb. The old link to this went stale (blog moved, etc.), so creating a new entry here as one way to find it. I cannot say if this works with CruiseControl.rb these days or not, as I haven't used Perforce since August 2007. I still use CruiseControl.rb, but now I'm fully on Git and GitHub. I highly recommend folks take a look at Git as a superior alternative to Perforce.
Anyway, you can get the code on GitHub, see my cruisecontrolrb_perforce project.