>perl lockdemo.pl
locker: flock LOCK_EX
locker: locked
locker: sleep 10
main: alarm 5
main: flock LOCK_EX                          ### The lock is acquired here
main: timeout at lockdemo.pl line 30.        ### before the timeout occurs.

main: 5 seconds have passed
locker: flock LOCK_UN
locker: unlocked