I don't want to use any non-standard modules if I can possibly avoid doing so.

By "non-standard modules", I assume you mean modules that must be downloaded from CPAN rather than the core modules that come with Perl. If that is what you mean, then I urge you to reconsider. The huge body of code in CPAN is one of the most compelling reasons for using Perl.

Consider that when you write your own code, you will be creating modules. What makes those modules more acceptable than the ones you can download from CPAN? The latter will have been peer-reviewed, installed and tested on multiple platforms. Will yours?

Also, I'm intrigued by your statement that you will develop on NT but deploy on UNIX. Why? You can obtain a Linux distribution at virtually no cost and set up a development environment that closely mirrors production. I would agree though that writing code that will run on multiple platforms is a laudable goal and readily achievable using Perl.