^和$只能定位在字串的开始和结束处,它们并不匹配嵌入的换行符,这种情况等同于A和,否则不仅仅匹配字串的开始和结束,也匹配刚好处在嵌入换行符前后的一个位置
v-lhb-db01:/root/perl# cat t1.pl
$_='a123a';
if ($_ =~ /Ad+z/){print "111
"};
v-lhb-db01:/root/perl# perl t1.pl
v-lhb-db01:/root/perl#
v-lhb-db01:/root/perl# cat t1.pl
$_='123a';
if ($_ =~ /Ad+z/){print "111
"};
v-lhb-db01:/root/perl# perl t1.pl
v-lhb-db01:/root/perl#
v-lhb-db01:/root/perl# cat t1.pl
$_='123';
if ($_ =~ /Ad+z/){print "111
"};
v-lhb-db01:/root/perl# perl t1.pl
11