[SYMBOL]
[A]
[B]
[C]
[D]
[E]
[F]
[G]
[H]
[I]
[J]
[L]
[M]
[N]
[O]
[P]
[Q]
[R]
[S]
[T]
[U]
[V]
[W]
[Z]
# comment
$ anchor
(...) parentheses
(?
...) subexpression grouping
(?>...) atomic grouping
(?<name>...) named capture
* greedy quantifier
*+ possessive quantifier
*? lazy quantifier
+ greedy quantifier
++ possessive quantifier
+? lazy quantifier
. (dot)
? greedy quantifier
?#... comment
?+ possessive quantifier
?? lazy quantifier
?i mode modifier
?if then | else
[...] character class
[^...] character class
\> metacharacter
\1
\A anchor
\b metacharacter
\B metacharacter
\cchar
\D
\d
\G anchor
\num
\p{prop}
\Q...\E (literal text span)
\S
\s
\unum
\Unum
\W
\w
\X
\x{num}
\xnum
\Z anchor
\z anchor
^ anchor
| alternation
|