当发出红色POST请求时，如何在标题中使用变量

我正试图用红色语言发出发帖请求

我必须传递一个带有授权的头，在发出请求并将其保存在变量

auth string

中之前，我要计算授权字符串的值

probe

精细打印

auth字符串

值

如果我在headers部分硬编码授权字符串，它会工作，但是当我尝试使用变量时，程序会退出

此代码带有硬编码的

授权：“基本c29tZX…

工作：

username: "someusernamestring"
password: "somepasswordstring"

url: to url! rejoin ["https://example.com/" username "/Account.json"]

auth-string: rejoin ["Basic " enbase/base rejoin [username ":" password] 64]
probe auth-string

response: write url [
        post [
        Content-Type: "application/x-www-form-urlencoded"
        Authorization: "Basic c29tZXVzZXJuYW1lc3RyaW5nOnNvbWVwYXNzd29yZHN0cmluZw=="
    ]
    {}    
]

print response

---

但是，这段代码，带有变量

Authorization:auth string

不起作用，程序退出，我看不到任何错误

username: "someusernamestring"
password: "somepasswordstring"

url: to url! rejoin ["https://example.com/" username "/Account.json"]

auth-string: rejoin ["Basic " enbase/base rejoin [username ":" password] 64]
probe auth-string

response: write url [
        post [
        Content-Type: "application/x-www-form-urlencoded"
        Authorization: auth-string
    ]
    {}    
]

print response

---

---

如何在headers部分中使用变量？

这应该像在Rebol中一样工作

response: write url compose/deep [
     post [
        Content-Type: "application/x-www-form-urlencoded"
        Authorization: (auth-string)
    ]
    {}    
]