The documentation for the 'die' function says the following:

Outside an eval, prints the value of LIST to STDERR and exits with the current value of $! (errno). If $! is 0 , exits with the value of ($?>> 8) (backtick `command` status).

Maybe you can help us to improve the Perl documentation by suggesting a change that would have made the answer to your question clearer to you when you read the documentation.