【Perl】正则表达式元字符

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1 simple

print "It matches\n" if "hello world" =~ /world/;
print "It doesn't match\n" if "hello world" !~ /word/;

$_ = "hello world";
print "it matches\n" if m{world};
print "it matches\n" if m!world!;
print "it matches\n" if m(world);
print "it matches\n" if m[world];

2 metacharacter


.	任意一个字符\n除外
+	重复>=1次
*	重复>=0次
?	重复<=1次
$	行尾
[]	字符类，匹配其中任意一个
()	组，在组中^$表行首行尾
\d	[0-9]
\D	[^0-9]
\s	空白字符
\S	[^\s]
\w	[0-9a-zA-Z]
\W	[^\w]
\b	单词边界
//i	case-insensitive
//g	多次匹配，函数pos记录其位置
s///	replace
s///r	返回替代结果但并不修改原来的值$_或用=~绑定的值
s///e	指明计算后的结果替代匹配的字符串

$x = "cat dog house";           # 3 words
while ($x =~ /(\w+)/g){
     print "Word is $1, ends at position ", pos $x, "\n";
}

# reverse all the words in a string
$x = "the cat in the hat";
$x =~ s/(\w+)/reverse $1/ge;   # $x contains "eht tac ni eht tah"

# convert percentage to decimal
$x = "A 39% hit rate";
$x =~ s!(\d+)%!$1/100!e;       # $x contains "A 0.39 hit rate"