How to make a tool giver that does not give the tool to players if they already have it?

How can I make a tool giver that detects the player's backpack and only give a tool to the player only if the player does not have the tool? If the player have the tool, the tool giver will not give the player the tool.

Here's the code that gives the player the tool multiple times:

function boop(Player)
 if not Player.Backpack:FindFirstChild(Gun) then
  local Tool = game.Lighting[Gun]:clone()
  Tool.Parent = Player.Backpack
 end
end
script.Parent.ClickDetector.MouseClick:Connect(boop)