Win32::Pipe seems to be ancient and unmaintained

Pipes are ancient. What makes you think it's unmaintained?

As far as I can tell, boilerplate open/write as per the Perl Cookbook only works for UNIX

I'd be surprised if it didn't work in Windows too.

opening/writing to a non-existent pipe creates a normal file

Not in Windows, since normal files can't start with \\.\pipe.

Furthermore, using «open '+<'» instead of «open '>'» would avoid that problem everywhere.