Sorry. I do not understand. I have 4 copies of windows.h and the rest on my system that came with various compilers I have installed.

The best guide I know of to using the free MS tools for building perl is Re: Building Perl with the free MSVC tools. I can't see a step that you haven't already followed, but maybe you can?

Be warned! I tried building Perl with BCC55 and Digitial Mars C++.

The makefile was modified at one point to ensure compataibility with BCC5.5, but that seemed to fall into decline almost immediately. I did eventually get it to build ater much frustration, but then the next build was released and I was back to square one.

I got nowhere at all with the Digital Mars compiler despite that it is an excellent, free compiler. Noone in the know has ever gone that route, and the incompatibilities are too deeply nested in the whole "Use a perl script to build a makefile the size of a house to run perl scripts to generate C files that get built using the makefile and command lines with a zillion (many times repeated) command line options and defines that make no sense at all" tortuous build process for me to unravell.

I suspect that trying watcom would be a similarly frustrating and fruitless execise.

The problem, from my perspective, is that there have only ever been about 10 people that ever understood the build process, and of those, only 3 or 4 are currently active on the Perl scene. Of them, none are interested in anything MS-related, so asking for help is like conversing with walls.

That said, maybe if you go to p5p and ask for help you'll get a better reception than I have.