Health script not working when modified?

Hello! I tried writing this very simple health script that I put in StarterCharacterScripts in order to replace the main one; I needed the regeneration value to be higher in case a value in a GUI was activated, to do so I used the GetPlayerFromCharacter in order to avoid using RemoteEvents. Seems not working and the script won't even work if normally put there, with no modifications. Mind helping me, please?

-- Gradually regenerates the Humanoid's Health over time.

local REGEN_RATE = 1/100 -- Regenerate this fraction of MaxHealth per second.
local REGEN_STEP = 1 -- Wait this long between each regeneration step.

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local Character = script.Parent
local Humanoid = Character:WaitForChild'Humanoid'
local Player = game:GetService("Players"):GetPlayerFromCharacter(Character)
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if Player.PlayerGui.IGMenu.Focus.Reg1.Unlocked.Value == true then
	local REGEN_RATE = 1.25/100
end

while true do
	while Humanoid.Health < Humanoid.MaxHealth do
		local dt = wait(REGEN_STEP)
		local dh = dt*REGEN_RATE*Humanoid.MaxHealth
		Humanoid.Health = math.min(Humanoid.Health + dh, Humanoid.MaxHealth)
	end
	Humanoid.HealthChanged:Wait()
end