What is Regex?
A regular expression (regex) is a pattern language for matching, searching, and replacing text. Patterns are built from literal characters and metacharacters — quantifiers (*, +, ?), character classes ([a-z]), anchors (^, $), and groups ((...)) — that describe a set of matching strings rather than one exact string.
Example
^[\w.-]+@[\w.-]+\.\w+$ matches a basic email address shape.
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