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Define regular expressions; clarify PCRE version #46033

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Jul 14, 2022
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Define regular expressions; clarify PCRE version #46033

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5 changes: 3 additions & 2 deletions doc/src/manual/strings.md
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Expand Up @@ -770,9 +770,10 @@ are some examples of non-standard string literals. Users and packages may also d
Further documentation is given in the [Metaprogramming](@ref meta-non-standard-string-literals) section.

## [Regular Expressions](@id man-regex-literals)
Sometimes you are not looking for an exact string, but a particular *pattern*. For example, suppose you are trying to extract a single date from a large text file. You don’t know what that date is (that’s why you are searching for it), but you do know it will look something like `YYYY-MM-DD`. Regular expressions allow you to specify these patterns and search for them.

Julia has Perl-compatible regular expressions (regexes), as provided by the [PCRE](https://www.pcre.org/)
library (a description of the syntax can be found [here](https://www.pcre.org/current/doc/html/pcre2syntax.html)). Regular expressions are related to strings in two ways: the obvious connection is that
Julia uses version 2 of Perl-compatible regular expressions (regexes), as provided by the [PCRE](https://www.pcre.org/)
library (see the [PCRE2 syntax description](https://www.pcre.org/current/doc/html/pcre2syntax.html) for more details). Regular expressions are related to strings in two ways: the obvious connection is that
regular expressions are used to find regular patterns in strings; the other connection is that
regular expressions are themselves input as strings, which are parsed into a state machine that
can be used to efficiently search for patterns in strings. In Julia, regular expressions are input
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