Listing all patterns that a regex matches

I am looking for a way to list all possible pa开发者_StackOverflow社区tterns from a finite regex (with no duplicates). Is there any source available?

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Although it won't cover some advanced features, and has its own share of other caveats, Regexp::Genex seems to be close to what you are looking for.

There's also this thread of PerlMonks which is relevant enough (as well as explaining how Regexp::Genex might not do for you, and some roll-yourself alternatives).

Otherwise, as per Jeffrey Friedl's Mastering Regular Expressions, you could use the /g modifier, coupled with the (?{CODE}) extension and a pattern that will never match, ala:

perl -E '$_ = 'Mastering Regular Expressions'; /(\p{L}*)(?{ say qq![$^N]! })(?!)/g;'

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A Haskell program based on Perl's Regexp::Genex can be found on Github and on Hackage.

According to the author, it was inspired by Regexp::Genex, but "uses a random-walk approach for character classes, instead of enumerating all possibilities."