I have found the same error in another module from RKHILL, DateTime::Event::Sunrise. This is RT ticket 34770, with a test case and a patch. This is due to the fact that sub _sun_RA_dec should return three values instead of just two and the calling sub _sunrise_sunset should not confuse the Right Ascension $sRA with the Sun-to-Earth distance in astronomical units $sr.
I guess the problem is the same with this module.