Without looking too close at your code (and without trying to run it) , I suspect its because of sharing STDIN/STDOUT/STDERR

So first thing I would try is to create detached processes without inheriting any handles with system_detached

If the popup you get is standard win32 error dialog, you can silence it on most NT5+ systems with https://metacpan.org/module/Win32API::File#SetErrorMode  use Win32API::File(); Win32API::File::SetErrorMode(2);