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http://kernel.org/doc/man-pages/online/pages/man7/signal.7.html
before commands after

http://kernel.org/doc/man-pages/online/pages/man7/signal.7.html Alternatively you could also insert the following in your code: use diagnostics; to get the explanations for every warning. See also perldoc perldiag for a detailed explanation of each warning and error.

$SIG{KILL} = sub { print "KILL received\n"; exit;};  # kill -9  cannot catch it
$SIG{INT}  = sub { print "INT received\n";};         # kill -2  or Ctrl-C
$SIG{TERM} = sub { print "TERM received\n"; exit;};  # kill -15
$SIG{TSTP} = sub { print "TSTP received\n";};        # kill -20 or Ctrl-Z