Why to shift bits "$? >> 8" when using Perl system function to execute command

Question

I have seen this in many places in Perl scripts:

system("binary");
$exit_code = ($? >> 8)
exit($exit_code)

1. Why should I use this? Is there an alternative way?

2. I am calling some binary in system(binary) which I created in C++, which does some stuff and if it fails it gives assert. When I reboot a Linux machine, the stuff which is going fails, and my binary generates assert as expected. But on the Perl side where I called it, it throws a 134 error code, which after 134 >> 8, becomes 0. Ultimately it is making my failure operation a success (which I don't want).

Answer 1

perldoc -f system snippet:

The return value is the exit status of the program as returned by the wait call. To get the actual exit value divide by 256.

You can check all the failure possibilities by inspecting $? like this:

$exit_value  = $? >> 8;
$signal_num  = $? & 127;
$dumped_core = $? & 128;