Regular Expression Meta-Characters, Meta-Brackets,and Meta-Sequences

Meta-Character	Description
^	This meta-character, the caret, matches the beginning of a string or, if the /m option isused, match the beginning of a line. It is one oftwo pattern anchors, the other anchor is the $.
.	This meta-character will match any single character except for the newline character unless the /s option is specified. If the /s option is specified, then the newline will also be matched.
$	This meta-character will match the end of a string or,if the /m option is used, match the end of a line.It is one of two pattern anchors; the other anchoris the ^.
|	This meta-character, called alternation, lets you specify two values that can cause the match to succe|ed. For instance, m/a|b/ means that the $_variable must contain the "a" or "b" character forthe match to succeed.
*	This meta-character indicates that the "thing" immediately to the left should be matched zero or more times in order to be evaluated as true (thus .*matches any number of characters).
+	This meta-character indicates that the "thing" immediately to the left should be matched one or more times in order to be evaluated as true.
?	This meta-character indicates that the "thing" immediately to the left should be matched zero or one times to be evaluated as true. When used inconjunction with the +, ?, or {n, m} meta-characters and brackets, it means that the regular expression should be non-greedy and match the smallest possible string.
Meta-Brackets	Description
()	The parentheses let you affect the order of pattern evaluation and act as a form of pattern memory. See the "Special Variables" chapter for moredetails.
(?...)	If a question mark immediately follows the left parentheses, it indicates that an extended mode component is being specified; this is new to Perl 5.
(?#comment)	Extension: comment is any text.
(?:regx)	Extension: regx is any regular expression but () are not saved as a backreference.
(?=regx)	Extension: Allows matching of zero-width positive lookahead characters (that is, the regular expression is matched but not returned as being matched).
(?!regx)	Extension: Allows matching of zero-width negative lookahead characters (that is, negated form of (=regx)).
(?options)	Extension: Applies the specified options to the pattern bypassing the need for the option to specified in the normal way. Valid options are: i (case insenstive), m (treat as multiple lines), s (treat as single line), and x (allow whitespace and comments).
{n, m}	Braces let you specify how many times the "thing" immediately to the left should be matched. {n} means that it should be matched exactly n times. {n,} means it must be matched at least n times. {n, m} means that it must be matched at least n times but not more than m times.
[]	Square brackets let you create a character class. For instance, m/[abc]/ evaluates to True if any of "a", "b", or "c" is contained in $_. The square brackets are a more readable alternative to the alternation meta-character.
Meta-Sequences	Description
\	This meta-character "escapes" the character which follows. This means that any special meaning normally attached to that character is ignored. For instance, if you need to include a dollar sign in a pattern, you must use \$ to avoid Perl's variable interpolation. Use \\ to specify the backslash character in your pattern.
\nnn	Any octal byte where nnn represents the octal number; this allows any character to be specified by its octal number.
\a	The alarm character; this is a special character which, when printed, produces a warning bell sound.
\A	This meta-sequence represents the beginning of the string. Its meaning is not affected by the /m option.
\b	This meta-sequence represents the backspace character inside a character class; otherwise, it represents a word boundary. A word boundary is the spot between word (\w) and non-word (\W) characters. Perl thinks that the \W meta-sequence matches the imaginary characters of the end of the string.
\B	Match a non-word boundary.
\cn	Any control character where n is the character (for example, \cY for Ctrl+Y).
\d	Match a single digit character.
\D	Match a single non-digit character.
\e	The escape character.
\E	Terminate the \L or \U sequence.
\f	The form feed character.
\G	Match only where the previous m//g left off.
\l	Change the next character to lowercase.
\L	Change the following characters to lowercase until a \E sequence is encountered.
\n	The newline character.
\Q	Quote regular expression meta-characters literally until the \E sequence is encountered.
\r	The carriage return character.
\s	Match a single whitespace character.
\S	Match a single non-whitespace character.
\t	The tab character.
\u	Change the next character to uppercase.
\U	Change the following characters to uppercase until a \E sequence is encountered.
\v	The vertical tab character.
\w	Match a single word character. Word characters are the alphanumeric and underscore characters.
\W	Match a single non-word character.
\xnn	Any hexadecimal byte.
\Z	This meta-sequence represents the end of the string. Its meaning is not affected by the /m option.
\$	The dollar character.
\@	The ampersand character.
\%	The percent character.