#!/usr/bin/perl
use strict;
use threads;
use warnings;
use feature 'say';
use Thread::Queue;

sub executeCommands {
    my ($commands) = @_;
    say $commands;
}

my $q = Thread::Queue->new();    # A new empty queue

# Set a size for a queue
$q->limit = 5;

# Worker thread
my $thr = threads->create(
    sub {
	# Thread will loop until no more work
	while (defined(my $item = $q->dequeue())) {
	    # Do work on $item
	    executeCommands($item);
	}
    }
    );

my @commands = ("Command_1", "Command_2");

# Send work to the thread
$q->enqueue(@commands);

{
    lock($q);   # Keep other threads from changing the queue's contents

    my @secondary_commands = ("Command_3", "Command_4");
    # Insert two items into the queue in the head
    $q->insert(-2, @secondary_commands);

    my $item = $q->peek();
    # do something with the items in queue if desired
    if ($item eq "Command_3") {
	my @third_commands = ("Command_5", "Command_6");
	# Insert two items into the queue just behind the peek
	$q->enqueue(@third_commands);
    }
}
# Queue is now unlocked

# Signal that there is no more work to be sent
$q->end();

# Join up with the thread when it finishes
$thr->join();

__END__

$ perl test.pl
Command_3
Command_4
Command_1
Command_2
Command_5
Command_6