in reply to Firefox Script
I admit to a general anti-Microsoft bias in much of my daily work but I have to give them this one. The fact that Windows has a general purpose scripting host architecture meaning that any scripting language that runs at all on the platform can also run in a whole variety of scripting-enabled applications is pretty damned cool.
I know almost nothing about Firefox internals, but I assume that their scripting engine is flexible enough that one could plug in support for other languages without outrageous amounts of pain. Not sure if anyone's done it with Perl, though.