. (period) Matches any character, except the end-of-line.

^ (caret) Matches the actual beginning-of-line position or the preceding line-delimiter character pair (also see [^] below for usage within a character class definition).

$ (dollar) Matches the end-of-line position.

| (stile) Specifies alternation (the OR operator), so that an expression on either side can match. Precedence is from left-to-right, as encountered in the expression.

? (question mark) Specifies that zero or one match of the preceding sub-pattern is allowed. Cannot be used with a Tag.

+ (plus) Specifies that one or more matches of the preceding sub-pattern are allowed. Cannot be used with a Tag.

* (asterisk) Specifies that zero or more matches of the preceding sub-pattern are allowed. Cannot be used with a Tag.

[ ] (square brackets) Identifies a user-defined class of characters, any of which will match: [abc] will match a, b, or c. Only three special metacharacters are recognized within a class definition, the caret (^) for complemented characters, the hyphen (-) for a range of characters, or one of the following \ backslash escape sequences:
\\ \- \] \e \f \n \q \r \t \v \x##

Any other use of a backslash within a class definition yields an undefined operation that should be avoided.

[-] (hyphen) The hyphen identifies a range of characters to match. For example, [a-f] will match a, b, c, d, e, or f.
Characters in an individual range must occur in the natural order as they appear in the character set. For example, [f-a] will match nothing.
Lists of characters, and one or more ranges of characters, may be intermixed in a single class definition. The start and end of a range may be specified by a literal character, or one of the \ backslash escape sequences:

\\ \- \] \e \f \n \q \r \t \v \x##
Any other use of a backslash within a class definition yields an undefined operation.
Multiple ranges in a class are valid. For example, [a-d2-5] matches a, b, c, d, 2, 3, 4, or 5.

When the hyphen is escaped, it is treated as a literal. For example, [a\-c] is a list, not a range, and matches a, -, or c due to the \ backslash escape sequence.

[^] (caret) When the caret appears as the first item in a class definition, it identifies a complemented class of characters, which will not match. For example, [^abc] matches any character except a, b, or c.
A range can also be specified for the complemented class. For example, [^a-z] matches any character except a through z.

A caret located in any position other than the first is treated as a literal character.

( ) (parentheses) Parentheses are used to match a Tag, or sub-pattern, within the full search pattern, and remember the match. The matched sub-pattern can be retrieved later in the mask, or in a replace operation, with \01 through \99, based upon the left-to-right position of the opening parentheses.
Parentheses may also be used to force precedence of evaluation with the alternation operator. For example, "(Begin)|(End)File" would match either "BeginFile" or "EndFile", but without the Tag designations, "Begin|EndFile" would only match either "BeginndFile" or "BegiEndFile".

Note: Parentheses may not be used with ? + * as any match repetition could cause the tag value to be ambiguous. To match repeated expressions, use parentheses followed by \01*.

\ (backslash). The escape operator (single-character quote). The following character will be treated as a literal value rather than being interpreted as a special character. Note that the character following the backslash must actually be a special character, as follows:

\b A word boundary. The start or end of a word, where a word is defined as one or more characters that include an alphabetic character (A-Z or a-z), a numeric character (0-9), and an underscore. For example, "abc_123" is considered a single word and "abc-123" is considered two words.

\c Case-sensitive search. Without the \c operator, the default is to ignore case when matching. Unlike some other implementations of regular expressions, case-insensitivity is recognized in all operations, even a range of characters such as "[6-Z]". The \c operator may appear at any position in the mask.
\e Escape character:
\f Formfeed character:
\n Linefeed (or newline)

\q Double-quote mark ("): example: "\qHello\q".
\r Carriage-return character
\s Shortest match character: The \s flag causes the shortest matching string to be returned, rather than the longest (the default). For example, when searching for the mask "abc.*abc" in "abcdabcabc", the default setting would return position 1 and length 10. With the \s switch set, it returns position 1 and length 7. This option may cause a slight increase in processing time.

\t Horizontal tab character

\v Vertical tab character

\x## Hex character code: Indicates that an ASCII code follows, given by two hexadecimal digits. For example, \xFF = ANSI 255. XX must be in the range 0 through 255.

\## Tag number: Evaluated as the characters matched by tag number ## (where ## is in the range 01 through 99, in decimal). Tags are implicitly numbered from 01 through 99, based upon the left-to-right position of the left parenthesis. "(…)w\01" would match "abcwabc" or "456w456".
Tags cannot be forward-referenced - that is, if a reference is made to any Tag that is not yet defined, a non-match is presumed.