function md5_sumhexa(k)    local md5_core = require "md5.core"    k = md5_core.sum(k)    return (string.gsub(k, ".",         function (c)             return string.format("%02x", string.byte(c))         end        )    )endprint(md5_sumhexa("Hello World!"))

md5.core.dll 是Windows平台二进制文件，下载地址：