在编写处理字符串的程序或网页时，经常会有查找符合某些复杂规则的字符串的需要。正则表达式就是用于描述这些规则的工具。换句话说，正则表达式就是记录文本规则的代码。-When writing programs or Web pages that deal with strings, there is often a need to find strings that meet certain complex rules. Regular expressions are the tools used to describe these rules. In other words, a regular expression is the code that records the text rules.