local function is_cusip(s)
    if #s != 9 then return false end
    local sum = 0
    for i = 1, 8 do
        local c = s[i]
        local v = switch true do
            case c >= '0' and c <= '9' -> c:byte() - 48
            case c >= 'A' and c <= 'Z' -> c:byte() - 55
            case c == "*" -> 36
            case c == "@" -> 37
            case c == "#" -> 38
            default        -> nil
        end
        if !v then return false end
        if i % 2 == 0 then v = v * 2 end  -- check if even as using 1-based indexing
        sum += v // 10 + v % 10
    end
    return s[9]:byte() - 48 == (10 - (sum % 10)) % 10
end

local candidates = {
    "037833100",
    "17275R102",
    "38259P508",
    "594918104",
    "68389X106",
    "68389X105"
}

for candidates as candidate do
    local b = is_cusip(candidate) ? "correct" : "incorrect"
    print($"{candidate} -> {b}")
end