I was tempted to write "RTFM", but in this case, the FM is not very fine. I guess that locn is latitude and longitude, as stated in a comment in the source:locn => undef, # ex: locn =>'82:30E 17:25N'
Reading the source is somewhat frightening. It contains at three undocumented packages without a reasonable prefix (Sun, Moon, Util), and its full of magic numbers without any explaining comment. There are lots of debugging artefacts. It completely lacks any sanity checks, and at least the example in the comment cited above is wrong. Looking at the code of sub _dolocn, the locn should not contain letters.
You should better treat Date::Indian as pre-alpha code, i.e. avoid it for production use.
You could try to contact the author, but I would not hope for an answer. His last upload is dated "27 Aug 2003".
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)