Scala program that sums two integers

object cli {
    val HELP_MSG = "Usage: arg1 - number 1, arg2 - number 2"

    def main(args: Array[String]): Unit = {
        if (args.length != 2) {
            System.err.println(HELP_MSG)
            return
        }

        var num1: Int = 0
        var num2: Int = 0

        try {
            num1 = args(0) toInt
        } catch {
            case ex: NumberFormatException =>
                System.err.println(ex)
                return
        }

        try {
            num2 = args(1) toInt
        } catch {
            case ex: NumberFormatException =>
                System.err.println(ex)
                return
        }

        printf("%d\n", num1 + num2)
    }
}