Is there a library that provides a near-complete solution for this? I looked around a bit and found many (many!) partial solutions on hackage, but nothing that really does it all. In coding it up for my own projects, however, I can't help but feel like I must be reinventing the wheel. What I want is something that will process command line options (this seems to be where most packages are targetted), environment variables, and settings files (possibly specified in options), and override/default appropriately. Did I miss something? If not, I'd like to see about fixing the situation, but very much want to avoid the whole "There were X libraries that didn't quite do it right; now there's X+1!" thing. Are there any opinions as to which of the many libraries is likely the best starting point if I'm going to contribute to one of them?