The literal byte with octal value n..n.

The NULL byte.

The literal byte with decimal value [1-9]..x.

The literal byte with hexadecimal value n..n.

Match the empty string at the beginning of a word.

Match the empty string at the end of a word.

Match the empty string at a word boundary.

Match the empty string provided it is not at a word boundary.

Match a word-constituent character, equivalent to [a:zA:Z0:9-].

Match a non-word-constituent character.

Literal alarm character.

Literal escape character.

Literal line feed.

Literal new line, equivalent to C's \n so it can be more than one character long.

Literal carriage return.

Literal tab.