(subexpression) | Captures the matched subexpression and assigns it a zero-based ordinal number. |
(?<name> subexpression) | Captures the matched subexpression into a named group. |
(?<name1-name2> subexpression) | Defines a balancing group definition. |
(?: subexpression) | Defines a noncapturing group. |
(?imnsx-imnsx: subexpression) | Applies or disables the specified options within subexpression. |
(?= subexpression) | Zero-width positive lookahead assertion. |
(?! subexpression) | Zero-width negative lookahead assertion. |
(?<= subexpression) | Zero-width positive lookbehind assertion. |
(?<! subexpression) | Zero-width negative lookbehind assertion. |
(?> subexpression) | Nonbacktracking (or "greedy") subexpression. |