The parenthesis around each digit grouping is vital-it allows us to refer to the matched characters inside those parentheses in the corresponding property.

每个数字组周围的括号非常重要，通过它可以在相应的属性中引用这些括号内的匹配字符。

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Each nested set of parentheses, counting from the left, incrementing at each left parenthesis is placed in the next special, numerical variable. For example.

每个嵌套的括号对，从左开始算起，每个左圆括号加一，放在下一个特殊的数字变量中。

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