How should I fix the laser damage from my code?

Hi guys, I'm doing my first game, basically it's a survival game, where you have machines that want to kill you, and you have to find a safe place. These machines are the loose lasers, two in each arm. The laser script has a problem, they were meant to deal damage, but they're not. They are lasers that are released in different directions. Here is the original script:

gun = script.Parent

function findNearestTorso(pos)
	local list = game.Workspace:children()
	local torso = nil
	local dist = 450
	local temp = nil
	local human = nil
	local temp2 = nil
	for x = 1, #list do
		temp2 = list[x]
		if (temp2.className == "Model") and (temp2 ~= script.Parent) then
			temp = temp2:findFirstChild("Torso")
			human = temp2:findFirstChild("Humanoid")
			if (temp ~= nil) and (human ~= nil) and (human.Health > 0) then
				if (temp.Position - pos).magnitude < dist then
					torso = temp
					dist = (temp.Position - pos).magnitude
				end
			end
		end
	end
	return torso
end

while true do
	wait(.5)
	local target = findNearestTorso(script.Parent.Position)
	if target ~= nil then
        local P = Instance.new("Part") 
		P.Name = "Laser" 
		P.formFactor = 0 
		P.Size = Vector3.new(10,10,10) 
                connection = script.Parent.Touched:connect(onTouch)
                local Distance = (target.Position - gun.Position).magnitude
		script.Parent.Mesh.Scale = Vector3.new(0.25, 0.25, Distance)
		P.CFrame = CFrame.new(gun.Position, target.Position)*CFrame.new(0, 0, -Distance/2)
		script.Parent.Mesh:Clone().Parent = P
                P.Parent = game.Workspace 
                P.BrickColor = BrickColor.new("Toothpaste")
		P.Transparency = 0
		P.Reflectance = 0
		P.Material = "Neon"
		P.Anchored = true
		P.CanCollide = true
		target.Parent.Humanoid.Health = target.Parent.Humanoid.Health - 100
		wait(1)
		P:remove()
	end
end

Well the idea is that the laser HAVE TO HURT IN THE TIME YOU GET ON, but I still do not know anything about roblox lua, so I'm in need of help. The idea is to deal damage when it hits, But when I hit no harm, I hope you guys help me.

You are connecting a function onTouch on line 34 to the Touched event. But onTouch has not been defined.

You need to define it:

local dmg = 100; --Variable for damage
local db = false; --Debounce

function onTouch(hit) --'hit' is the object the laser has hit
	if db then return end --Debounce logic
	db = true;
	--Check for player
	local hum = hit.Parent:FindFirstChild("Humanoid");
	if hum then
		--Damage player
		hum.Health = hum.Health - dmg;
	end
	db = false;
end