#!/usr/bin/perl

use strict;
use Fcntl qw( :flock );
use Getopt::Long;

GetOptions( 'test' => \my $option_test );

print "Running $0\n";
check_process() if ( ! defined( $option_test ) );
sleep 30;
print "Running $0\n";


sub check_process {
    open( SELF, '<', $0 )
      || die "Error: Cannot open $0 for locking - $!\n";
    flock( SELF, LOCK_EX | LOCK_NB )
      || die "Error: Another $0 is already running.\n";

    return 1;
}

##</code><code>##

$ perl test.pl  --> should run if there is no test.pl running.
$ perl test.pl  ---> should abort if there is a test.pl running already.
$ perl test.pl --test  --> should run even if test.pl is already running.
$ perl test.pl --test  --> should abort if there is a (test.pl --test) running as well.