A note. Often some of the biggest maintainability questions can be solved by asking a question you hadn't thought of. For instance you are asking about the best code for converting between a type number and a corresponding name in Perl. I look at that and immediately ask, "Why are you using a numerical code in Perl?"

My answer to that question would be, "Unless forced by external circumstances, I wouldn't." Numerical codes are inherently less maintainable to program with than string descriptions. For a type code, perhaps string descriptions which go through a function that catches any typos.

And, of course, if I don't have numerical codes floating around, I no longer need to think about the most maintainable way to write the conversion code...