Contrary to popular belief, IPC::Open3 does not use fork under Win32. If indeed your open3() even comes from that module (you didn't say).

And I see no hints as to what $main->fileevent is. It looks vaguely like an interface to 4-argument select. If so, then you probably don't know that 4-argument select in Win32 only works on sockets and so can't be used on pipes like you are trying to do there.

        - tye (but my friends call me "Tye")