为了启动的纪念 perl 正则

有时想不起来，记一下：（源自perl by example edition 4）

Character Class: Single Characters and Digits
.	Matches any character except a newline
[a–z0–9]	Matches any single character in set
[^a–z0–9]	Matches any single character not in set
\d	Matches one digit
\D	Matches a nondigit, same as [^0–9]
\w	Matches an alphanumeric (word) character
\W	Matches a nonalphanumeric (nonword) character
Character Class: Whitespace Characters
\s	Matches a whitespace character, such as spaces, tabs, and newlines
\S	Matches nonwhitespace character
\n	Matches a newline
\r	Matches a return
\t	Matches a tab
\f	Matches a form feed
\b	Matches a backspace
\0	Matches a null character
Character Class: Anchored Characters
\b	Matches a word boundary (when not inside [ ])
\B	Matches a nonword boundary
^	Matches to beginning of line
$	Matches to end of line
\A	Matches the beginning of the string only
\Z	Matches the end of the string or line
\z	Matches the end of string only
\G	Matches where previous m//g left off
Character Class: Repeated Characters
x?	Matches 0 or 1 x
x*	Matches 0 or more occurrences of x
x+	Matches 1 or more occurrences of x
(xyz)+	Matches 1 or more patterns of xyz
x{m,n}	Matches at least m occurrences of x and no more than n occurrences of x
Character Class: Alternative Characters
was|were|will	Matches one of was, were, or will
Character Class: Remembered Characters
(string)	Used for backreferencing
\1 or $1	Matches first set of parentheses
\2 or $2	Matches second set of parentheses
\3 or $3	Matches third set of parentheses
Character Class: Miscellaneous Characters
\12	Matches that octal value, up to \377
\x811	Matches that hex value
\cX	Matches that control character; e.g., \cC is -C and \cV is -V
\e	Matches the ASCII ESC character, not backslash
\E	Marks the end of changing case with \U, \L, or \Q
\l	Lowercase the next character only
\L	Lowercase characters until the end of the string or until \E
\N	Matches that named character; e.g., \N{greek:Beta}
\p{PROPERTY}	Matches any character with the named property; e.g., \p{IsAlpha}/
\P{PROPERTY}	Matches any character without the named property
\Q	Quote metacharacters until \E
\u	Titlecase next character only
\U	Uppercase until \E
\x{NUMBER}	Matches Unicode NUMBER given in hexadecimal
\X	Matches Unicode "combining character sequence" string
\[	Matches that metacharacter
\\	Matches a backslash