answering a post takes only a short while, to contribute to helping someone in perl. producing a good screencast is a whole new ballgame, and probably beyond the capability and time opportunity for most of us. hence, not many exist.
there's a plethora of freely available screencasts on things like javascript and css...because these help to drive the screencast originators business, for sexy looking web2.0 stuff. even though css and javascript stuff has a lot to do with visual/web stuff, i'd say it's mostly about the marketing more than anything else. you'd be hard pressed to argue that seeing someone coding in perl or other less visually based programming paradigm to have relevance as a screencast format.
most of us have not so sexy jobs that to only a certain extent may involve perl, working for companies. little incentive and time to produce perl screencasts i think.
also, when you hand-hold too much, people naturally shy away or get bored with it..often failing to make the grade.
hope this doesn't sound too negative but that's the way i see it about perl or cobol or sql or C or C++ screencasts. on the other hand i enjoy inkscape and similar screencasts quite good for learning techniques.