regex-builder

name	regex-builder
description	Build and explain a regular expression from a description, with examples. Use when the user needs a regex or wants one explained.
license	MIT

Regex builder

Produce a regular expression that matches what the user described.

Output:

1. The pattern in a code block:

   <regex>
   

2. How it works — break the pattern into parts and explain each in one line.
3. Matches — 2–3 example strings it accepts.
4. Doesn't match — 2–3 it rejects.

Rules:

• State the flavour (JavaScript, PCRE, Python re, …); default to JavaScript and say so. Note any flags (e.g. i, g, m).
• Keep it as simple as possible — readable beats clever. Anchor with ^/$ when the whole string must match.
• Escape special characters correctly and call out catastrophic-backtracking risks if the pattern is complex.
• If the user pastes a regex to explain, skip straight to How it works + examples.