jIH:
{QIn tetlhvam vImuvbe'pu'} I didn't join this list, and this (my not joining) is completed. voragh: I have no idea what this "translation" is supposed to mean. Do you mean that you failed to join the list (e.g. you tried repeatedly but the sign-up subroutine isn't working)? Perhaps if you provide a little context for each example I'd have a better idea of what you're asking.
The way I understand the translation of this example is "sometime in the past I tried/wanted/decided to join this list, but because of some reason, eventually I didn't. And now, at the time I'm speaking this sentence, my "not joining" is complete". Unfortunately, I can't explain any further my understanding of this example.. I'm at a loss myself with regards to the use of {-be'} with the {-pu'} or {-ta'}. I don't know; perhaps I'm overthinking this. From what I understand though, the {-pu'be'} is far more common, so I'll just place from now on the {-be'} after the aspect suffix without trying too much to analyze the meaning. ~ nI'ghma