Ah, but you need to put it in a *.h file that will be included by the Posix module so that it will know that your vendor now does define WNOWAIT.

(short pause while I double check something before opening my big mouth -- something I almost never do)

Posix.pm #include's perl.h which #include's config.h so the definition of WNOHANG needs to be added to each of the win32/config_H.* files except win32/config_h.PL.

Thanks a ton for doing this!