Perl 正则表达式的奇技淫巧1（perl语言正则表达式）

"\K" escape 来自于Regexp::Keep, 在perl5.10 版本中加入到变成perl 正则表达式的一部分：

通常用来处理正则表达式的性能问题， 意思是在正则表达式的匹配从\K之后的开始：

先上例子：

# slow and inefficient

my $r = "abc.def.ghi.jkl";

$r =~ s/(.*)\..*/$1/;

# fast and efficient

my $s = "abc.def.ghi.jkl";

$s =~ s/.*\K\..*//;

更多例子

:意思是所有被匹配的字符串， 可以看到下面的例子中一直在向后退，原因是\K位置的移动。

"alphabet" =~ /([^aeiou][a-z][aeiou])[a-z]/;

# $1 is "pha", is "phab"

"alphabet" =~ /\K([^aeiou][a-z][aeiou])[a-z]/;

# $1 is "pha", is "phab"

"alphabet" =~ /([^aeiou]\K[a-z][aeiou])[a-z]/;

# $1 is "pha", is "hab"

"alphabet" =~ /([^aeiou][a-z]\K[aeiou])[a-z]/;

# $1 is "pha", is "ab"

"alphabet" =~ /([^aeiou][a-z][aeiou])\K[a-z]/;

# $1 is "pha", is "b"

"alphabet" =~ /([^aeiou][a-z][aeiou])[a-z]\K/;

# $1 is "pha", is ""