Sorry, kind of screwed up there - what I was trying to do was plot a handle that comes from a call to the polar(...) command. plot2svg works fine for figure handles. I retract my fix, but not the whole dying-without-plot2svg thing.
By the way, this is the most awesome and necessary script I've ever used. When it stopped working I wanted to die and thought the world around me was crumbling to pieces, leaving me shattered and vulnerable to the cruel biddings of Adobe Illustrator.
But now those days are over, I can breathe a breath of joy knowing that I can continue to use Inkscape for making figures! Hurrah!