I'm trying to make this sprint script use Left Control instead of sprint. Is this right?

I'm trying to make this sprint script use Left Control instead of sprint. But it doesn't work Is this right?

local p = game.Players.LocalPlayer
local c = p.Character
local m = p:GetMouse()

local sprint = false

local t,f = true,false

local w,a,s,d = f,f,f,f
local wt = 0

m.KeyDown:connect(function(key)
    if key == '50' then
        sprint = t
    end
    if key == 'w' then
        w = t
    end
    if key == 'a' then
        a = t
    end
    if key == 's' then
        s = t
    end
    if key == 'd' then
        d = t
    end
end)
m.KeyUp:connect(function(key)
    if key == '50' then
        sprint = f
    end
    if key == 'w' then
        w = f
    end
    if key == 'a' then
        a = f
    end
    if key == 's' then
        s = f
    end
    if key == 'd' then
        d = f
    end
end)

while wait() do
    wt = wt - .01
    if wt <= 0 then
        if script.Parent.Frame.Bar.Size.X.Scale < .9 then
            script.Parent.Frame.Bar.Size = script.Parent.Frame.Bar.Size + UDim2.new(.009,0,0,0)
        end
    end
    if w or a or s or d then
        if script.Parent.Frame.Bar.Size.X.Scale > 0 and sprint then
            script.Parent.Frame.Bar.Size = script.Parent.Frame.Bar.Size - UDim2.new(.009,0,0,0)
            c.Humanoid.WalkSpeed = 26
        end
    end
    if sprint then
        wt = 1.3
    end
    if not w and not a and not s and not d then c.Humanoid.WalkSpeed = 16 end
    if not sprint then c.Humanoid.WalkSpeed = 16 end
    if script.Parent.Frame.Bar.Size.X.Scale <= 0 then c.Humanoid.WalkSpeed = 16 end
end