command ("/slow") {
    val sender = this.sender
    if (sender is Player) {
        listOf("slow", "slow digging", "slow falling").forEach {
            sender.effect(it, 20 * 10)
        }
        sender.message("You are now slooooowwww....")
    } else {
        sender.message("Only players can execute this command!")
    }
}