function formatarNumero(valor)
  local formatado = valor
  while true do  
    formatado, n = string.gsub(formatado, "^(-?%d+)(%d%d%d)", '%1.%2')
    if ( n ==0 ) then
      break
    end
  end
  return formatado
end
 
print(formatarNumero(1))
print(formatarNumero(10))
print(formatarNumero(100))
print(formatarNumero(1000))
print(formatarNumero(10000))
print(formatarNumero(100000))
print(formatarNumero(1000000))
print(formatarNumero(10000000))
print(formatarNumero(100000000))
print(formatarNumero(1000000000))
print(formatarNumero(-123))

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