关于正则表达式中“#{}”的疑惑

关于正则表达式中“#{}”的疑惑

Programming php?name=Ruby" onclick="tagshow(event)" class="t_tag">Ruby 中有这么一段,没看明白是什么意思。自己写了几行代码php?name=%B2%E2%CA%D4" onclick="tagshow(event)" class="t_tag">测试,也没发现正则表达式的“/o”选项有什么作用。
哪位大虾能解释一下,或者给几行代码演示一下?
引用:
Substitutions

#{...}
Performs an expression substitution, as with strings. By default, the substitution is performed each time a regular expression literal is evaluated. With the /o option, it is performed just the first time.
再好好看pr,上面说得很清楚
就是初次匹配