Thank you all. If I say "brakło mi pieniędzy" everyone would interpret that in the exact same way as "zabrakło mi pieniędzy"?
yes - as I stated these tend to be used interchangeably
What about the form "braknie"? I did some Google searching, and it seems to work like an imperfective verb. Could it be that it's considered perfective in the past tense and imperfective in the present, something like braknie = brakuje and brakło = zabrakło? Or perhaps I'm just confused now.
I think your intuitions are quite right - perfective and imperfective are not that clearly opposite in the future (in Polish) as they are in the pastPójdziesz do kina? Będziesz szedł do kina? and Idziesz do kina
(with enough context) can well be used (and are used) interchangeably - the semantic differences are slight here - it is really a matter of nuance - Pójdziesz do kina?
sugests that a more definite answer is expected, while będziesz szedł do kina
is a more indirect form to ask a question and eventually Idziesz do kina?
is at present the form of choice for asking someone if s/he is going to the movies in a stated time (on a stated day for example)