Meta characters in regular expressions

For more information about Perl regular expressions, see the Perl Programming Documentation website, and search for perlre.

Table 1. Meta characters for Perl regular expressions.. The table lists some of the standard escape characters that can be used in Perl regular expressions. These expressions are supported in the EmailPlusRule and EmailPlusTemplate records.
Meta character	Description
`\`	Marks the next character as either a special character or a literal. For example, `n` matches the character n, whereas `\n` matches a newline character. The sequence `\\` matches \ and `\(` matches (.
`^`	Matches the beginning of input.
`$`	Matches the end of input.
`*`	Matches the preceding character zero or more times. For example, `zo` matches either z or zoo*.
`+`	Matches the preceding character one or more times. For example, `zo+` matches zoo but not z.
`?`	Matches the preceding character zero or one time. For example, `a?ve`? matches the ve in never.
`.`	Matches any single character except a newline character.
`(pattern)`	Matches a pattern and remembers the match. The matched substring can be retrieved from the resulting matches collection by using this code: `Item [0]...[n]`. To match parentheses characters ( ), use $ or $.
`x\|y`	Matches either `x` or `y`. For example, `z\|wood` matches z or wood. `(z\|w)oo` matches zoo or wood.
`{n}`	`n` is a non-negative integer. Matches exactly `n` times. For example, `o{2}` does not match the o in Bob, but matches the first two os in foooood.
`{n,}`	In this expression, `n` is a non-negative integer. Matches the preceding character at least `n` times. For example, `o{2,}` does not match the o in Bob and matches all the os in foooood. The `o{1,}` expression is equivalent to `o+` and `o{0,`} is equivalent to `o*`.
`{n,m}`	The `m` and `n` variables are non-negative integers. Matches the preceding character at least `n` and at most `m` times. For example, `o{1,3}` matches the first three os in fooooood. The `o{0,1}` expression is equivalent to `o?`.
`[xyz]`	A character set. Matches any one of the enclosed characters. For example, `[abc]` matches the a in plain.
`[^xyz]`	A negative character set. Matches any character that is not enclosed. For example, `[^abc]` matches the p in plain.
`[a-z]`	A range of characters. Matches any character in the specified range. For example, `[a-z]` matches any lowercase alphabetic character in the English alphabet.
`[^m-z]`	A negative range of characters. Matches any character that is not in the specified range. For example, `[m-z]` matches any character that is not in the range m through z.
`\A`	Matches only at beginning of a string.
`\b`	Matches a word boundary, that is, the position between a word and a space. For example, `er\b` matches the er in never but not the er in verb.
`\B`	Matches a nonword boundary. The `ear\B` expression matches the ear* in never early.
`\d`	Matches a digit character.
`\D`	Matches a non-digit character.
`\f`	Matches a form-feed character.
`\n`	Matches a newline character.
`\r`	Matches a carriage return character.
`\s`	Matches any white space including spaces, tabs, form-feed characters, and so on.
`\S`	Matches any non-white space character.
`\t`	Matches a tab character.
`\v`	Matches a vertical tab character.
`\w`	Matches any word character including underscore. This expression is equivalent to `[A-Za-z0-9_]`.
`\W`	Matches any non-word character. This expression is equivalent to `[^A-Za-z0-9_]`.
`\z`	Matches only the end of a string.
`\Z`	Matches only the end of a string, or before a newline character at the end.