Detecting a Value that is already in a list?

I have been struggling with preventing duplicate walls.

The function below takes two points and makes a wall between them. It then added that walls position to list01

The for loop in this function is what I've recently added and its failed at getting the desired result.

local wallOffset --Offset for midpoint Y axis
local list01 =  {} -- a table for holding each wall that's been placed

--Function for creating walls
local function createWall(last, currentPos)
    --Create a wall and size it between current and last pillar
    local wall = Instance.new("Part")
    wall.Name = "Wall"
    wall.Size = Vector3.new((last-currentPos).Magnitude,9,1)
    --(X,Y,Z) of the midpoint of the wall
    local midX = (last.X + currentPos.X)/2
    local midY = (last.Y + currentPos.Y)/2 - wallOffset
    local midZ = (last.Z + currentPos.Z)/2
    local orientation = (last - currentPos).Unit:Cross(Vector3.new(0,1,0))
    local CFramePos = Vector3.new(midX, midY, midZ)
    --Move wall to Midpoint
    wall.CFrame = CFrame.new(CFramePos, CFramePos + orientation)
    --print out the last pillars POS and the current pillars POS
    print("Last:",last, "Current:",currentPos)
    wall.Anchored = true
    wall.CanCollide = false --Change soon, add to teams disabled collision group
    --Put walls POS in list or destroy wall if already in list.
    for index = 1, #list01 do
        local value = list01[index]
        if value == wall.Position then
            wall:Destroy()
            print("wall destroyed")
            break
        else
            table.insert(list01, wall.Position)
            print("Wasn't Destroyed, added to table")
        end
    end
    print("List number: ", table.getn(list01))

end

I can see that I need to change the for loop(or possibly it's the wrong approach), right now if the first value isn't the same it will add the wall POS to the list regardless if the wall does exist in the list at another index. But if I remove the else statement then I'm not sure where to 'table.insert' when it is a new wall.

That's where I'm at and any help is always appreciated.