Groups and Ranges

.

Any character except new line (\n)

(a|b)

a or b

(...)

Group

(?:...)

Passive (non-capturing) group

[abc]

Range (a or b or c)

[^abc]

Not (a or b or c)

[a-q]

Lower case letter from a to q

[A-Q]

Upper case letter from A to Q

[0-7]

Digit from 0 to 7

\x

Group/subpattern number "x"