| (...) | Group a regular expression to override default operator precedence. |
| (?r-s:pattern) |
Apply option r and omit option s while interpreting pattern. Options may be zero or more of the characters i, s, or x.
Options
| Option | Description |
| i | Case insensitive. |
| -i | Case sensitive. |
| s | Alters the meaning of '.' to match any character whatsoever. |
| -s | Alters the meaning of '.' to match any character except '\n'. |
| x | Ignores comments and whitespace in patterns. Whitespace is ignored unless it is backslash-escaped, contained within ""s, or appears inside a character range. |
These options can be applied globally at the rules level by passing a combination of the bit flags to the lexer.
|
| (?# comment ) | Omit everything within (). The first ) character encountered ends the pattern. It is not possible for the comment to contain a ) character. The comment may span lines. |