You mean Proc::PID::File? Have a look at File::Lockfile but it's not that much easier. 
use Proc::PID::File;
die "Already running!" if Proc::PID::File->running();

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Doesn't get much easier than that, does it? Edit: ups, ww beat me to it :)

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

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