You appear to be using the same state handler for POE::Wheel::Run's CloseEvent and for the SIGCHLD. They have different values in their ARG0 .. $#_ as well. You should definitely have separate state handlers for these.

I tend to use sig_child() for handling CHLD instead of sig() as it gives you more flexibility in how one handles different types of child within the same session. It also implicitly keeps a session alive until the given child has been reaped, which sig() doesn't.