That's a pretty good list.

I would add some things that I have also found helpful :

1. If you are working on a script of any complexity, modularise. Split functionality out into other modules that don't depend on CGI environment, the CGI itself just instantiates an object, passes it the CGI object, and calls "print" (for example) on that object to produce the output. The great advantage of this is that you can now run a seperate test script on your module (using Test::Simple for instance) and get the complex stuff working right, method by method before worrying about the CGI part. (Some people like fancy names for this kind of thing, I quite like "common sense".)

(This may also have an advantage that moving to mod_perl later (if you want to) will be easier. So I'm told. Don't know yet because I haven't gotten there ...)

2. If you have a lot of HTML, use a template package like Mason or FastTemplate. Get the HTML out of your code and life will start to get easier. You will also reduce the number of bugs you bring in due to making small changes in the way your application looks.