|Think about Loose Coupling|
Ah, thanks. _PROTECT_FROM_CLOSE does a lot more than that ("If this flag is set, calling the CloseHandle function will not close the object handle"). But if 'exec' doesn't have its own flag for "don't close upon exec", I could see implementing it this way (and can see some problems that such a choice presents).
I was conflating the "don't close when creating a subprocess" with the "don't close when exec()ing cases". But then, Windows doesn't have fork() nor exec() so there really is only the "don't close when creating a subprocess", which is what _INHERIT is for. (Perl's exec on (non-Cygwin) Windows actually creates a subprocess and then has the parent process exit.)
Perhaps you should be setting _INHERIT instead?
Also, your code doesn't appear useful for the use-case you proposed. You don't want some "Console" handle for talking over some protocol, surely. So write some code that creates a pipe or uses a socket and then try to give that file descriptor to the child (probably using _INHERIT not _PROTECT_FROM_CLOSE, I would bet) and see how that works.
Indeed, the point of including SetHandleInformation() in Win32API::File was exactly for the purpose of letting other programs use handles that your Perl script opened. I think how I've done that successfully in the past was via _INHERIT, but, to be honest, I'm not completely sure at the moment.
Please let us know how it works out.