前面我們都是在整個(gè)輸入的字符串中做匹配憨琳，而沒有考慮在字符串中的哪個(gè)具體的位置做匹配辅髓，比如只在行首做匹配株灸，只在行末做匹配吼和。Boundary matcher就是用來限定匹配位置的。
| Boundary Construct | Description |
|---|---|
| ^ | The beginning of a line |
| $ | The end of a line |
| \b | A word boundary |
| \B | A non-word boundary |
| \A | The beginning of the input |
| \G | The end of the previous match |
| \Z | The end of the input but for the final terminator, if any |
| \z | The end of the input |
需要注意^和\A的區(qū)別句伶，因?yàn)檩斎肟赡懿恢挂恍小?/p>
Boundary Matcher
