Greetings.

The project is completed including a release on CPAN. To ensure a given script is executing once, the following is how to do it using Mutex. That will block until obtaining an exclusive lock. A false value is returned if the timeout is reached, and a true value otherwise.

use Mutex;

my $mutex = Mutex->new( path => $0 );

# terminate script if a previous instance is still running
exit unless $mutex->timedwait( 2 );

...
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Regards, Mario

Edit: Updated the CPAN link to point to the 1.001 release.