Regex Tutorial - Lookahead and Lookbehind Zero-Length AssertionsLookahead and lookbehind, collectively called “lookaroundâ€, are zero-length assertions just like the start and end of line, and start and end of word anchors explained earlier in this tutorial. The difference is that lookaround actually matches characters, but then gives up the match, returning only the result: match or no match. That is why they are called “assertionsâ€. They do not consume charac
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