Regular Expressions
-------------------

   Regular expressions are the extended kind found in `egrep'.  They
are composed of characters as follows:

`C'
     matches the character C (assuming C is a character with no special
     meaning in regexps).

`\C'
     matches the literal character C.

`.'
     matches any character except newline.

`^'
     matches the beginning of a line or a string.

`$'
     matches the end of a line or a string.

`[ABC...]'
     matches any of the characters ABC... (character class).

`[^ABC...]'
     matches any character except ABC... and newline (negated character
     class).

`R1|R2'
     matches either R1 or R2 (alternation).

`R1R2'
     matches R1, and then R2 (concatenation).

`R+'
     matches one or more R's.

`R*'
     matches zero or more R's.

`R?'
     matches zero or one R's.

`(R)'
     matches R (grouping).

   See Regular Expressions as Patterns: Regexp, for a more detailed
explanation of regular expressions.

   The escape sequences allowed in string constants are also valid in
regular expressions (see Constant Expressions: Constants.).