### Matching Rules for Basic Regular Expressions

The following rules apply within a Basic Regular Expression (BRE):

- An ordinary character matches itself. The simplest form of regular expression is a string of characters with no special meaning.
- A special character preceded by a backslash matches itself. For BREs, the special characters are:

         . [ \ * ^ $

  In general, it is best not to precede ordinary characters by a backslash, except in special situations such as backreferencing, grouping , and specifying a number of occurrences.

- A period (.) without a backslash matches any single character.
- An expression within square brackets ( [ ] ), a bracket expression, matches a single character or collating element.

Regular Expressions

Additional Syntax Specifiers for Basic Regular Expressions