Data::Alias was generally broken in 5.18.x (CPAN Testers Reports confirm this).
This seemed to affect quite a few people: there've been a number of posts about this.
Version 1.17 of Data::Alias appears to have fixed the problem; again, CPAN Testers Reports seem to confirm this.
By rote learning.
Via Genetic memory.
It's provided by my firmware.
I just remember them.
Thirty days hath September
My computer gets it right, usually.
I just ask someone else.
Someone punches me on the first of the month.
Results (151 votes),