It would probably take a bit of wrapping but Devel::ebug::HTTP might be a good starting point for this. I played with it a bit last fall or summer and it looked pretty interesting (it's built on top of Catalyst so there are naturally tons of dependencies that must be present in order to install it). Devel::ebug::HTTP is an extention of Devel::ebug which is an attempt to refactor the stock perl debugger. It provides a really slick (AJAX) web interface that (IIRC) even allows you to step backwards in your script. I only dabbled with it for a couple of days before letting it sit long enough that I've not yet come back to it.

It might be worth a look to see if it would be customizable enough to act more like an interactive shell rather than a full-featured debugger.

-- Brian