Learn to use regular expressions by following RegexTip. From @JohnDCook.
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Finding all English words with four or more consecutive vowels: johndcook.com/blog/2019/10/1…
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To include a literal ^ in a character class, don't put it first: /[^^]/ matches any char except '^'.
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? means a character or expression is optional, i.e. zero or one occurrences. Example: /ab?c/ matches 'ac' and 'abc' but not 'abbc'.
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Languages have minor variations in their regex support. @RegexTip mostly sticks to the common features of Perl, C#, Python, JavaScript, ...
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Regex matches are usually not anchored. If you forget ^ and $, your pattern can match inside a larger string unexpectedly.
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Unicode Regular Expressions Standard: unicode.org/reports/tr18/
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Comparing regular expressions in Perl, Python, and Emacs johndcook.com/blog/regex-per…
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A hyphen is a range marker only *inside* a character class and not at the edges. /[a-z-]/ matches letters or '-'; /[a-z]/ is just letters.
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Prefer using libraries for phone numbers, URLs, emails, etc. when quick-and-dirty isn't good enough correctness matters.
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Performance tip: if you can, start your pattern with a literal prefix. Engines can skip quickly to the prefix before doing heavier work.
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Escaping is context-dependent. Outside [...], '.' is special; inside a character class, [.] is just a period. Can be clearer than \.
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Use a non-capturing group when you don't need backreferences: /(?:cat|dog)s?/ matches 'cat', 'cats', 'dog', 'dogs' without creating a capture group.
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'Everybody stand back. I know regular expressions.' xkcd.com/208/
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Regular expressions in Haskell wiki.haskell.org/Regular_exp…
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Properties such as \p{Alphabetic} can be easier to read than [A-Za-z]. Works better with internationalization as well.
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