Shell script that uses an flock on itself to avoid multiple instances being run

onlyone.sh

#!/bin/bash
# Based on https://plus.google.com/+RandalLSchwartz/posts/QcrqvT3mUdy

exec 200< "$0"
if ! perl -MFcntl=LOCK_EX,LOCK_NB -e 'open(FH, "<&=200"); flock(FH, LOCK_EX|LOCK_NB) or exit 1'; then
    echo "There can be only one!"
    exit 1
fi

echo "Locked and safe"
sleep 10
echo "Unlocking and exiting"
exit 0