The syntax for a regular expression e0 is
e3: literal | charclass | '.' | '^' | '$' | '(' e0 ')' e2: e3 | e2 REP REP: '*' | '+' | '?' e1: e2 | e1 e2 e0: e1 | e0 '|' e1
A literal is any non-metacharacter, or a metacharacter (one of .*+?()|\^$), or the delimiter preceded by \.
A charclass is a nonempty string s bracketed [s] (or [^s]); it matches any character in (or not in) s. A negated character class never matches newline. A substring a-b, with a and b in ascending order, stands for the inclusive range of characters between a and b. In s, the metacharacters -, ], an initial ^, and the regular expression delimiter must be preceded by a \; other metacharacters have no special meaning and may appear unescaped.
A . matches any character.
A ^ matches the beginning of a line; $ matches the end of the line.
The REP operators match zero or more (*), one or more (+), zero or one (?), instances respectively of the preceding regular expression e2.
A concatenated regular expression, e1e2, matches a match to e1 followed by a match to e2.
An alternative regular expression, e0|e1, matches either a match to e0 or a match to e1.
A match to any part of a regular expression extends as far as possible without preventing a match to the remainder of the regular expression.
|REGEXP(6 )||Rev: Thu Feb 15 14:43:48 GMT 2007|