Standard Siye uses perfective -na and imperfective -ma (my translation of the perfective as a past tense and imperfective as a present tense in examples is for clarity's sake). The irrealis mood changes the distinction to one of contrafactual versus possibility (unless there's a converbal suffix that requires the irrealis mood, in which case it's a bit more complicated). The positive and negative interrogative suffixes -umo and -ukumo can do strange things also. A prospective in Siye is formed with the converbal suffix -(u)lu- and an aspect marker - with the perfective, it means "I just have", with the imperfective "I am about to".

le laye lumni liyo pomikem elipulunama.

le-0 laye lum-ni liyo pomi-kem-0 e-i-li-pu-ulu-na-ma

1-NOM woman slender-COM food day-LOC-ABS 4-3-eat.IMPV-SG-TNS-DIR.SUPER-POS.IMPV-REALIS

I am about to eat lunch with a slender athletic woman.

Which I am, so examples will have to come later.