package HighLander;
use strict;
use Fcntl qw( LOCK_EX LOCK_NB );

open(our $fh, '<', $0)
  or die("Can't open \"$0\": $!\n");

unless ( flock($fh, LOCK_EX|LOCK_NB )) {
  print "Another instance of \"$0\" is already running. Exiting...\n";
  exit(0);
}

1;