Code.swift

import Cocoa

let concurrentQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)
let serialQueue = dispatch_queue_create("queue", 0)

let array = [ "'0'", "'1'", "'2'", "'3'", "'4'", "'5'", "'6'", "'7'", "'8'", "'9'", "'10'" ]

for x in 1..10 {
    let str = array[x];
    dispatch_async(serialQueue) { println("serial: \(x) \(str)") }
    dispatch_async(concurrentQueue) { println("concurrent: \(x) \(str)") }
}

dispatch_main()

Result

concurrent: 8 '8'
concurrent: 6 '6'
concurrent: 1 '1'
concurrent: 2 '2'
serial: 1 '1'
concurrent: 7 '7'
concurcroennctcu:or nr3ce un'rt3r:'e 
n5t :' 54' 
'4'
consceurriraeln:t :2  9' 2''9
'
serial: 3 '3'
serial: 4 '4'
serial: 5 '5'
serial: 6 '6'
serial: 7 '7'
serial: 8 '8'
serial: 9 '9'