in reply to what's the favorite report system for perl web application?

You can pretty much use anything. We've previously used ColdFusion (okay, bad idea, but we needed good-looking reports fast and it was quicker to get a ColdFusion contractor to knock them out; ditched it because we evolved to the point it was no longer dependable or fast enough), a custom-built Perl solution (worked, but not flexible enough to keep up), and are now switching over to Jaspersoft, which looks to be both flexible enough and fast enough for the time being.

Choose whatever you're comfortable with, that will keep up with the demands, and that runs quickly enough to get the reports out in the time you need. On a quick Google I don't see a specific report-builder framework for Dojo. If you know Birt and it meets your needs, no reason to not use it.