Searching through ps output is not really the right way to do it on Unix. It's time-consuming and error-prone--someone may create a link to the program with a different name or there may be two different programs with the same name.

Fortunately there's a simple solution that works on Unix and Windows:

#!perl -w
use strict;

use Fcntl qw(LOCK_EX LOCK_NB);
my $lockfile = "/someabsolutepath/writeabledirectory/lockfile";
open LOCKFILE, ">", $lockfile or die  "Cannot open lockfile\n";

if (!flock(LOCKFILE, LOCK_EX|LOCK_NB)) {
  print STDERR "Another copy of application is already running\n";
  exit(0);
}
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