I think when he said "cmd" he meant something like $cmd which contains the command. I don't think this question has anything to do with windows, he probably should have said, system('my_long_command_here &') or something.
Comment on Re^2: Run the process in the background
I know. I never assumed he was refering to cmd.exe. (I assumed the opposite, since cmd.exe doesn't accept host names are arguments.) I described the most likely scenario given the lack of details posted by the OP, and the solution for that problem.