No, backtick does not "return the return code." Backtick (the qx// operator) returns the string of any output that the child process sends to STDOUT. The system() call does return the return code.

But he wants to abandon everything else in this script, flush all buffers, close all files, release all resources, and at the last possible moment, to jump to the beginning of a new program instead. The exec() function is just a little heavy-handed since it doesn't do all the cleanup first.