I used locks in these case 

#Open a file
open(SINGLECHECK,">.server1.pid") or $file->log("$0:Cannot open the lo
+ck file $!\n");
#Lock the file in exclusive mode and non-blocking mode so that no two 
+same demon will run.
flock(SINGLECHECK, LOCK_EX|LOCK_NB) or ($file->log("$0:server is Alrea
+dy running\n") and exit(1));

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In reply to Re: Abort if instance already running? by lakshmananindia
in thread Abort if instance already running? by pileofrogs

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