假设 C#:
StringCollection resultList = new StringCollection();
Regex regexObj = new Regex("^.*<(?:/?b|/?em|/?su[pb]|/?[ou]l|/?li|span style=\"text-decoration: underline;\" data-mce-style=\"text-decoration: underline;\"|/span)>(?! ).*$", RegexOptions.Multiline);
Match matchResult = regexObj.Match(subjectString);
while (matchResult.Success) {
    resultList.Add(matchResult.Value);
    matchResult = matchResult.NextMatch();
} 
将返回文件中的所有行,其中列表中的标签之一后至少有一个空格。
输入:
This </b> is <b> OK
This <b> is </b>not OK
Neither <b>is </b> this.
输出:
This <b> is </b>not OK
Neither <b>is </b> this.
解释:
^      # Start of line
.*     # Match any number of characters except newlines
<      # Match a <
(?:    # Either match a...
 /?b   #  b or /b
|      # or 
 /?em  #  em or /em
|...   # etc. etc.
)      # End of alternation
>      # Match a >
(?! )  # Assert that no space follows
.*     # Match any number of characters until...
$      # End of line