Regular expressions are based on POSIX EREs (Extended Regular Expressions). Regexps are composed of characters. Here is a short-list of them all:
matches the character c (assuming c is none of the characters listed below).
matches the literal character c.
matches any character.
matches the beginning of a string.
matches the end of a string.
matches any of the characters abc… (character list).
matches any character in the character class keyword.
Allowable classes are
matches the multi-character collating element. Gcal does not currently support collating symbols.
matches any of the equivalent characters in list. Gcal does not currently support equivalence classes.
matches any character except abc… (negated resp. complemented character list).
matches either r1 or r2 (alternation).
matches r1, and then r2 (concatenation).
matches one or more r’s.
matches zero or more r’s.
matches zero or one r’s.
matches r (grouping).
matches at least n, n to any number, or n to m occurrences of r (interval expressions).
matches the empty string at either the beginning or the end of a word.
matches the empty string within a word.
matches the empty string at the beginning of a word.
matches the empty string at the end of a word.
matches any word-constituent character (alphanumeric characters and the underscore).
matches any character that is not word-constituent.
matches the empty string at the beginning of a buffer81.
matches the empty string at the end of a buffer.