The one I'd recomend looking at is Circlemud. As far as text processing, you're not going to find useful information being that you're writing this is perl and circlemud is written in C; but as far as the structure and implemenataion of races, skills, spells, etc.. it would be an excelent refrence. IMO, things like their magic system could be improved.. and it might have being that I haven't looked at this code in over 2 years. But there's probably a lot there that you can draw from since this has been an evergreen type of project for many years.

As far as having a bunch of constant data declared, It's pretty common. In perl, I'm not exactly sure of the socially acceptable way of doing this, but if you look at the header files for any (well written) C program, you have declaration upon declaration of constant data. Wether you put that at the top of your script or put it in another file that you include or require is a matter of style and what's socially acceptable. Personally, with something as large as this, I'd farm out all the constant declarations to a seperate file. It helps to keep things as simple as possible. I'd also try to keep all systems in a seperate file. For instance.. all combat related subs would be in one file.. magic in another.. communication in yet another.. etc..

Hope this helps..
Rich