in reply to Developing code to be a module
Good question.
I think about whether the module's going to represent an object, whether it's going to be an API, or whether it's just going to be a collection of useful, related code.
Once I've figured that out, I can start writing the module, ideally writing tests as I go, so that I have some confidence that new stuff doesn't break the old stuff.
The three standard modules I start with are strict, warn and Carp, and I always write code with error-checking in place -- that way I never have to remember to add it later.
And I also use git, committing early and often. I can't tell you how many times way back when I hacked on some code, realized it was a disaster, and longed to go back to an earlier, working version. With git, you can totally do that.