It depends on what you want, as somwone already said here, if you are looking for outputs from your script then the back ticks are your friends. but output from system commands is a little different especially if you want the errors returned from it. to get the error message itself you can use the back ticks but to get the error code use the system():

$errorCode = system("SYSCOMMAND");
[download]

you can also use $! for retrieving the error message after the execution of a command.

Hotshot