#! perl -lw
use strict;
use Fcntl ':flock';
open my $fh, "<", "whatever" or die $!;

flock $fh, LOCK_EX;
flock $fh, LOCK_EX;

##</code><code>##

open my $fh, "<", "whatever" or die $!;
flock $fh, LOCK_EX;

my $pid = open my $pip, "|-";
die "open(): $!" unless defined $pid;
if ($pid > 0) { close $pip }
else          { flock($fh,LOCK_EX); print "got the lock"}

##</code><code>##

if ($pid > 0) { flock($fh,LOCK_EX); print "got the lock" }
else          { sleep(20) }