Thanks a million, NiLuJe, the tweaked version seems to have solved my problem! Thank you!!
Now that I am trying to put the plugin to good use, I have a how-to question.
I'd like to create collections based on the "languages" meta-data item. I do not have a tag for it, as tags became superfluous for this purpose after the introduction of the "languages" category/identifier/... (what is it called properly?).
How can I do that?