Basically, I am comparing each character across a number of same-length strings

You might get a better answer if you explained how this character comparison works (compare each character to what)?

In Perl often a regex (regular expression) is what you need for this sort of situation. Also it is seldom necessary to use numeric indicies (or course, seldom does not mean "never"). Perl has a lot of cool iterators to process arrays and other structures of things without using an explicit index. That is actually very cool since right at the top of common coding errors is the "off by one" problem.

Anyway you dived pretty quick into asking how to access a string of characters as an array and it might be that what you really need to know is actually something else.