$SIG{INT}  = sub { print "You zapped me!\n"; };

print "Try to zap me with ^C, I dare you!\n";
sleep 5;

# normally warnings are not fatal
warn "This is your last warning\n";
# make warnings fatal
$SIG{__WARN__} = sub { print "Died fron the warning @_\n"; exit };
# now warnings will be fatal
warn "I warned you!";

print "You will never read this, because the last warning killed me!";