Read perlfunc :) It states:

die LIST

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). If "($? >> 8)" is 0, exits with 255.

Example:

rhesa@schutz:~$ perl -e '$!=3; die "whoa: $!"'
whoa: No such process at -e line 1.
rhesa@schutz:~$ echo "exit=$?"
exit=3
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