This table lists the metacharacters that may be used in {{Value(…MATCH= regexp )}} and {{Value(…SUBSTITUTE= regexp )}}.

Metacharacter Meaning
. Matches any single character.
[ ] Indicates a character class. Matches any character inside the brackets (for example, [abc] matches a, b, and c).
^ If this metacharacter occurs at the start of a character class, it negates the character class. A negated character class matches any character except those inside the brackets (for example, [^abc] matches all characters except a, b, and c).

If ^ is at the beginning of the regular expression, it matches the beginning of the input (for example, ^[abc] will only match input that begins with a, b, or c).

- In a character class, indicates a range of characters (for example, [0-9] matches any of the digits 0 through 9).
? Indicates that the preceding expression is optional: it matches once or not at all (for example, [0-9][0-9]? matches 2 and 12).
+ Indicates that the preceding expression matches one or more times (for example, [0-9]+ matches 1, 13, 666, and so on).
* Indicates that the preceding expression matches zero or more times.
??, +?, *? Non-greedy versions of ?, +, and *. These operators match as little as possible, unlike the greedy versions which match as much as possible. Example: given the input <abc><def>, <.*?> matches <abc> while <.*> matches <abc><def>.
( ) Grouping operator. Example: (\d+,)*\d+ matches a list of numbers separated by commas (such as 1 or 1,23,456).
{ } Indicates a match group.
\ Escape character: interpret the next character literally (for example, [0-9]+ matches one or more digits, but [0-9]\+ matches a digit followed by a plus character). Also used for abbreviations (such as \a for any alphanumeric character; see the table below).

If \ is followed by a number n , it matches the n th match group (starting from 0). Example:

<{.*?}>.*?</\0> matches <head>Contents</head>.
$ At the end of a regular expression, this character matches the end of the input. Example: [0-9]$ matches a digit at the end of the input.
| Alternation operator: separates two expressions, exactly one of which matches (for example, T|the matches The or the).
! Negation operator: the expression following ! does not match the input. Example: a!b matches a not followed by b.