Dodanie do skryptu lokalizacji

Witam jak dodać do tego skryptu żeby będąc na danym świecie nie można byłoby teleportować się na ten świat jeszcze raz i wyświetlała by się wiadomość "Jesteś już na tym świecie" 

on right click on entity:
	if display name of entity is "Kapitan":
		set {_gui} to chest inventory with 3 rows named "&a&lKapitan"
		set slot 0 of {_gui} to paper named "&aPodruz do Miasta"
		set slot 1 of {_gui} to paper named "&aPodruz na Wyspe piekla"
		set slot 2 of {_gui} to paper named "&aPodruz do Netheru" with lore "&aWymagany: &6Bilet do Netheru"
		open {_gui} to player
on inventory click:
	event-inventory is not player's inventory
	if name of event-inventory is "&a&lKapitan":
		cancel event
		if clicked slot is 0:
			teleport player to location 1, 60, 1 in world "world"
			close player's inventory
		if clicked slot is 1:
			teleport player to location 1, 60, 1 in world "wyspa"
			close player's inventory
		if clicked slot is 2:
			if player doesn't have 1 paper named "&6Bilet do Netheru" with lore "&6Do wykorzystania u Kapitana":
				send "&cNie posiadasz biletu!" to player
			else:
				cancel event
			if player have 1 paper named "&6Bilet do Netheru" with lore "&6Do wykorzystania u Kapitana":
				remove 1 paper named "&6Bilet do Netheru" with lore "&6Do wykorzystania u Kapitana" from player's inventory
				close player's inventory
				teleport player to location 1, 60, 1 in world "world_nether"
				send "&aDotarles do Netheru" to player
			clear {inventory::teleporty::%player%}