Regex — the patterns you actually use

## Anchors
`^` — start of line
`$` — end of line
`\b` — word boundary

## Char classes
`\d` — digit
`\w` — word char (alnum + _)
`\s` — whitespace
`.` — any char
`[abc]` — a, b, or c
`[^abc]` — NOT a, b, or c
`[a-z]` — range

## Quantifiers
`*` — 0 or more
`+` — 1 or more
`?` — 0 or 1
`{3}` — exactly 3
`{3,5}` — 3 to 5

## Groups + alternation
`(abc)` — group
`(?:abc)` — non-capturing group
`abc|def` — abc OR def
`(\d+)-(\d+)` — capture groups, refer with $1, $2

## Common patterns
`\d{3}-\d{4}` — phone-ish
`\b[A-Z]{2,}\b` — all-caps acronyms
`^[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,}$` — email-ish (case-insensitive flag)