Describe What You Want to Match and Let Claude Write the Regex

Nobody enjoys writing regex from scratch. Instead of staring at a cheat sheet, just tell Claude what you need to match and it writes the pattern for you — correctly, with an explanation, in the flavor your language uses.

> write a regex that matches UK phone numbers in any common format —
> with or without the country code, with spaces or dashes or no separators

Claude gives you the pattern, breaks down what each part does, and shows it matching against realistic examples so you can verify it handles the cases you care about.

This works for any complexity level:

> match email addresses but only from .edu domains

> extract the version number from strings like "v2.4.1" or "version 3.0"

> validate a password has at least 8 chars, one uppercase, one number,
> and one special character

> match markdown links and capture the text and URL separately

Where this really shines is when you already have sample data. Paste a few real examples and tell Claude what to extract:

> here are some log lines from our app:
> [2024-03-15 09:42:13] ERROR: Connection timeout after 30s (host=db-primary)
> [2024-03-15 09:42:14] WARN: Retry attempt 2/3 (host=db-primary)
> [2024-03-15 09:42:15] INFO: Connection restored (host=db-primary)
>
> write a regex that captures the timestamp, log level, message, and host

Claude writes the pattern, shows the named capture groups, and demonstrates it working against each line — so you can paste it into your code with confidence.

You can also ask Claude to explain an existing regex you inherited. Paste that unreadable 200-character monster from your codebase and Claude translates it back to English.

Never write regex by trial and error again — describe the pattern you need and Claude gets it right the first time.

via Claude Code