Perl——正则表达式(四) 查找替换s///

一. 介绍

使用?s/regex/replacement/modifiers 进行查找替换

二. 实例

(1) s///

$f = "'quoted words'";
#进行模式匹配,下面方法去除''单引号
if($f =~ s/^'(.*)'$/$1/) { #true,$1指的是引用了第一组(.*)的内容,^$这两个字符用来表示开始与结束

	print "matches","n"; # mathces
	print $f,"n";        # quoted words
	                      # 注意 标量$f 匹配后本身内容发生了变化
}

用它进行匹配后,原始标量的值不会发生变化，可以把新值赋值给一个新的标量

$f = "'quoted words'";
#进行模式匹配,下面方法去除''单引号
$n = $f =~ s/^'(.*)'$/$1/r;

print "matches","n";
print $f,"n"; # quoted words   # 注意 标量$f 匹配后本身内容无变化
	
print $n,"n"; # 'quoted words' # 注意 $n

$z = "time hcat to feed the cat hcat";
$z =~ s/cat/AAA/g;#替换多次
print $z,"n"; #结果为 time hAAA to feed the AAA hAAA

# 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"