您可以将模式编写为：

(?i)[A-Z]+(?:\+[A-Z]+)*$

• • 说明**
• (?i)不区分大小写的内联修饰符
• [A-Z]+匹配1+字符A-Z
• (?:\+[A-Z]+)*（可选）重复匹配+，并再次匹配1+字符A-Z
• $字符串结束

有关匹配项，请参见regex101 demo：
例如

import re

predeterminedList = ["foo", "bar"]
strings = ["foo", "foo+bar", "foo+bar+baz", "test+abc"]
pattern = r"(?i)[A-Z]+(?:\+[A-Z]+)*$"

for s in strings:
    m = re.match(pattern, s)
    if m:
        words = m.group().split("+")
        intersect = bool(set(words) & set(predeterminedList))
        fmt = ','.join(predeterminedList)
        if intersect:
            print(f"'{s}' contains at least one of '{fmt}'")
        else:
            print(f"'{s}' contains none of '{fmt}'")

另一个选项是创建列出备选项的动态模式：

(?i)^(?:[A-Z]+\+)*(?:foo|bar)(?:\+[A-Z]+)*$

示例

import re

predeterminedList = ["foo", "bar"]
strings = ["foo", "foo+bar", "foo+bar+baz", "test+abc"]
pattern = rf"(?i)^(?:[A-Z]+\+)*(?:{'|'.join(predeterminedList)})(?:\+[A-Z]+)*$"

for s in strings:
    m = re.match(pattern, s)
    fmt = ','.join(predeterminedList)
    if m:
        print(f"'{s}' contains at least one of '{fmt}'")
    else:
        print(f"'{s}' contains none of '{fmt}'")

两者都将输出：

'foo' contains at least one of 'foo,bar'
'foo+bar' contains at least one of 'foo,bar'
'foo+bar+baz' contains at least one of 'foo,bar'
'test+abc' contains none of 'foo,bar'

我建议使用lookarounds的方法稍有不同：
图案：(?<=^|\+)(?=foo|baz)[^+]+
图案说明：
(?<=^|\+)-正向后查找-Assert前面的文本既不是^（字符串的开头）也不是+（我们的“字分隔符”）。
(?=foo|baz)-正向前看-Assert以下文本匹配（预定义列表中）一个单词
[^+]+-匹配+以外的一个或多个字符
Regex demo