Recipe
NL → regex with explanation
Turn plain-English descriptions into precise regular expressions with inline commentary so you understand every token.
Prompt
Write a regex that matches a valid IPv4 address. After the regex, add a line-by-line breakdown of what each part does.Output
^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}
(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$^ — anchor to start of string
(?:...) — non-capturing group for one octet
25[0-5] — matches 250–255
2[0-4][0-9] — matches 200–249
[01]?[0-9][0-9]? — matches 0–199 with optional leading digits
\\. — literal dot separator
{3} — repeat the octet-plus-dot group three times
$ — anchor to end of string
Tips
- Ask for the breakdown explicitly — models skip it otherwise.
- Specify the regex flavor (PCRE, JavaScript, Python) if it matters.
- Request non-capturing groups for cleaner match results.