Regex XSLT中的正则表达式

有人能帮我理解下面XSLT中的常规表达式吗

regexp:match(test-graph.api.example.com, '(?=CN).*\.(.*)(\.)(.*)(?<=com)', 'i')

输出是什么以及如何解释这个正则表达式

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请让我知道

应该这样读：

(?=CN).*\.(.*)(\.)(.*)(?<=com)

参见

.* matches any character (except for line terminators)
    * Quantifier — Matches between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\. matches the character . literally (case sensitive)
1st Capturing Group (.*)
.* matches any character (except for line terminators)
    * Quantifier — Matches between zero and unlimited times, as many times as possible, giving back as needed (greedy)
2nd Capturing Group (\.)
\. matches the character . literally
3rd Capturing Group (.*)
.* matches any character (except for line terminators)
    * Quantifier — Matches between zero and unlimited times, as many times as possible, giving back as needed (greedy)
Positive Lookbehind (?<=com)
Assert that the Regex below matches
com matches the characters com literally