摘要：
1 匹配行首 '^' or '\A'断言区别：当使用m（多行）修饰符时，^匹配每行的行首，而\A仍然仅在整个字符串的开头进行匹配eg：$_ = "this is\na multi file"; s/^/BOL/g; #BOL this is #BOL a multi file s/\A/BOL/g; #BOL this is #a multi file2 匹配行尾 '$' or '\z'/'\Z''$' 在行尾之前进行匹配$_ = 'Here is some text\n 阅读全文
