use Fcntl ':flock';

open my $fh, "+<", $0 or exit;
exit unless flock $0, LOCK_EX | LOCK_NB;

[download]
Note that depending on your OS and how you call the program, a second open may fail (and then, the flock isn't necessary).

In reply to Re: Easiest way to protect process from duplication. by JavaFan
in thread [Solved]Easiest way to protect process from duplication. by kazak

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