use strict;
use warnings;
use threads;
use threads::shared;
$|++;

my $DONE :shared = 0;
my $lock :shared;

my $execMethod = $ARGV[0] || 0;
if($execMethod !~ /[12345]/){
	print "Must pass an exec method:\n";
	print "1 = backticks\n";
	print "2 = backticks synchronized\n";
	print "3 = open\n";
	print "4 = open synchronized\n";
	print "5 = system\n";
	exit 1;
}
sub execute{
	my $cmd = shift;
	if($execMethod == 1){
		`$cmd`
	}elsif($execMethod == 2){
		lock $lock;
		`$cmd`
	}elsif($execMethod == 3){
		open(my $fs, "-|", $cmd);
		foreach(<$fs>){};
		close $fs;
	}elsif($execMethod == 4){
		lock $lock;
		open(my $fs, "-|", $cmd);
		foreach(<$fs>){};
		close $fs;
	}elsif($execMethod == 5){
		system($cmd . ">nul");
	}
}

sub worker{
	while(!$DONE){
		execute('echo hello world');
	}
}
my @workers = map threads->create( \&worker), (1..30);
print "Press <enter> to terminate\n";
<STDIN>;
$DONE = 1;

$_->join() for @workers;