Do you know the author of the code you are trying to maintain? Do you have an estimate of their abilities as a perl programmer? What other languages did they code in?
The reason I ask is because you often find strange idioms in perl scripts written by people who are used to writing in shell, C or another language, and because TIMTOWTDI and perl is tolerant of these idioms it works and the programmer leaves them in and gets used to writing their code that way. (For example, see node 927269 where the author looks to be used to writing C.)