Here's a variation that uses the __DATA__ handle. 
use Fcntl qw(LOCK_EX LOCK_NB);
die "Another instance is already running" unless flock DATA, LOCK_EX|L
+OCK_NB;

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In reply to Re^2: Easiest way to protect process from duplication. by gnosti
in thread [Solved]Easiest way to protect process from duplication. by kazak

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