I worked through these once a day (or was it per week?) several years ago, and it really ingrained regex rule into my brain.

See also: https://jimbly.github.io/regex-crossword/

For Python, I wrote a TUI app with 100+ interactive exercises: https://github.com/learnbyexample/TUI-apps/blob/main/PyRegexExercises (covers both re and regex modules)

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