问题如下 :
http://zhidao.baidu.com/question/501928970.html?push=keyword
解决如下:
#! /usr/bin/perl -w use strict; my $string = "abc r=3 def r=3 test r=3 over"; print $string,"\n"; $string =~ s/(?<=def r=)\d/5/; #?<= 匹配exp后面的位置 print $string,"\n"; $string = "abc r=3 def r=3 test r=3 over"; #?= 匹配exp前面的位置 $string =~ s/\d(?= def)/5/; print $string,"\n"; $string = "abc r=3 def r=3 test r=3 over"; #?! 匹配后面跟的不是exp的位置 $string =~ s/\d(?! def)/5/; print $string,"\n"; $string = "abc r=3 def r=3 test r=3 over"; #?<! 匹配前面不是exp的位置 $string =~ s/\d(?<! def)/5/; print $string,"\n";