The sad thing (for me) is I went through almost every part of the code and I understand about 90% of what's going on at every interval point (set by me). Yet, I can't seem to have an idea of what username is required by the program.

The point is that as I showed you with a randomly picked snippet, translation in more compact, more directly understandable Perl is easy albeit annoying and time consuming. I suppose most of us are plainly not interested in doing so for the whole program although I suggest you do. Perhaps some degree of automated "simplifying" could be possible, but however simple the code is, I would expect that writing a program doing that would take more time and more efforts than proceeding manually. Thus I recommend you to take a step by step approach simplifying the original program gradually into "saner" Perl, making sure at each step that the program is still syntactically correct and for what is possible that it also runs just fine. When you're stuck at a point where you can't go on anymore, then you may have a more interesting Perl question and people may be more willing to help you.