So there's no way to work around this using IPC::System::Simple?

I don't know.

Should I just revert back to using qx// and forget about it?

If qx// works, its probably because its creating a console  cmd /x /c ...your stuff here .. as in  C:\WINDOWS\system32\cmd.EXE

So you might be able to persuade IPC::System::Simple to use the shell (cmd.exe) , but it kind of defeats the purpose of using IPC::System::Simple

Or you might use Win32::ShellQuote like I showed to launch cmd.exe safely with qx{}

Or you might make it work if you manage to use Win32::Console to allocate a console

FWIW, I think the real problem is win32 webservers which spawn procs without an allocated console (IMHO dumb), but I haven't even seen this issue discussed anywhere