Unlike other IO commands, system returns 0 on sucess, making the system() or die ... construct rather useless.

the documentation elaborates quite a bit on the correct way to check for errors. Read it (both of you :-).

Also I'd never, ever consider running the web server as root, not even for testing. A much saner approach would be to add a sudo rule that allows the www or www-data user to execute just that one command. But the whole idea seems flawed to me. Remote management systems exist.