How to match the same text twice — backreferences with \1

The closing quote must equal the opening one; the repeated word must be the same word.

Patterns use the syntax shared by PCRE / Python / JavaScript; engine differences are flagged in the cheatsheet where they matter. Test any pattern at regex101.com — and pick the matching engine.

(['"]).*?\1
# "hello" or 'hello' — closing quote must match the opening one
(\w+)\s+\1
# repeated word: "the the"

Regex Cheatsheet one-page card — patterns that actually work — The full one-page card — Regex Cheatsheet. Get the complete cheatsheet on GitHub