Grouping

Grouping
Sequence Description
(...) 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. i means case-insensitive. -i means 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.