If you have the possibility of running parts of KDE on the machine that is going to generate the images, you could use the kwebdesktop program to use the khtml-Engine (the same as in Konqueror, i.e. a /very/ good one ;) to get you a rendered image of your site ...
It is intended for use as a desktop background generator, but it should work for your case just as well :
kankoku:~$ kwebdesktop --help
Usage: kwebdesktop Qt-options KDE-options width height file URL
Width of the image to create
Height of the image to create
Filename where to dump the output in png format.
URL to open
It is part of kdebase. Hope this helps; it's not strictly perl ;)