After extensive googling and simply trying something out on a whim, here's what I came up with that works:

$x = $image->Annotate(font=>'/usr/share/fonts/bitstream/Vera.ttf', fil
+l=>'#00FF00', pointsize=>12, x=>10, y=>30, text=>$text); warn "$x" if
+ $x;
[download]

Thanks for your help.