Why do I have HealthChanged Errors? [EDITED]

First I Created a localscript with the code:

local plr=game.Players.LocalPlayer
local chr=plr.Character
local hm=chr.Humanoid

b=game.ReplicatedStorage.b:Clone()

hm.Health.HealthChanged:connect(function(heth)
    local changed=math.abs(hm.Health-heth)
        --]] What should I Add?
    if b then
        b.Parent=chr.Torso
    end
end)

What should I add, in order to tell if a Player lost some health?

Please respect that I am a Beginner in need of knowledge