您可以使用分支重置组以匹配空字符串，如果整个 $ c>情态动词后面的词，否则为概念动词：

You may use a branch reset group to match an empty string if there is not as a whole word after a modal verb, or a notional verb otherwise:

\b(I|you|he|she|it|we|they|this|that|these|those)\s+(can|should|would|could|must|want to|have to|had to|might)\s+\K(?|(?=not\b)()|([^ß\W]\w{2,15})\b)

请参见 regex演示

详细信息

• \b -单词边界


• （我|您|他|她|它|我们|他们|这个|那个|那些|那些）-组1中的代词之一


• \s + -1+空格（它已经作为相邻两边的单词边界t个组）


• （可以|应该|将|必须|想要|必须|必须|可能）-情态动词之一


• \s + -1+空格


• \K -匹配重置运算符


• （？|（？= not\b）（）|（[^ ß\W] \w {2,15}）\b）-与
  
  
  
  
  • 匹配的分支重置组（？= not\b）（）-如果在整个单词的右边紧接有 not ，请捕获第3组中的空字符串
  
  
  • | -或（在此为其他）
  
  
  • （[[^ ß\W] \w {2,15}）\b -将以外的任何其他字符char匹配并捕获到组3中ß，然后是2到15个带有字符边界的单词字符。
  
  
  • \b - a word boundary
  • (I|you|he|she|it|we|they|this|that|these|those) - one of the pronouns in the group 1
  • \s+ - 1+ whitespaces (it is already acting as a word boundary on both sides of the adjacent groups)
  • (can|should|would|could|must|want to|have to|had to|might) - one ofthe modal verbs
  • \s+ - 1+ whitespaces
  • \K - match reset operator
  • (?|(?=not\b)()|([^ß\W]\w{2,15})\b) - the branch reset group matching either
    • (?=not\b)() - if there is not as whole word immediately to the right, capture an empty string into Group 3
    • | - or (here, else)
    • ([^ß\W]\w{2,15})\b - match and capture into Group 3 any word char other than ß and then 2 to 15 word chars with a word boundary to follow.

    请注意，（？m）- PCRE_MULTILINE -仅在您需要 ^ 和 $ 匹配行的开始和结束而不是整个字符串。由于您的模式没有此类锚点，因此（？m）是多余的。

    Note that (?m) - PCRE_MULTILINE - is only necessary if you want your ^ and $ outside of character classes match start and end of lines rather than the whole string. Since your pattern has no such anchors, (?m) is redundant.