代码如下，比如想把 ab+ 的都找出来，比如 gsub 的例子里，都替换成大写的了； 但是怎么从 MatchData 实例里得到第 n（n>1）组匹配结果的信息呢？ 类似 php 或者 Java 那样，能取得每组匹配的信息？

类似这个问题：https://www.ruby-forum.com/topic/1435305

irb(main):146:0> a="abbcdefgabbbbcdefg"
=> "abbcdefgabbbbcdefg"
irb(main):147:0> b = a.gsub(/(ab+)/){|y| y.upcase}
=> "ABBcdefgABBBBcdefg"
irb(main):148:0> a="abbcdefgabbbbcdefg"
=> "abbcdefgabbbbcdefg"
irb(main):149:0> x =/(ab+)/.match a
=> #<MatchData "abb" 1:"abb">
irb(main):150:0> x[0]
=> "abb"
irb(main):151:0> x[1]
=> "abb"
irb(main):152:0> x[2]
=> nil
irb(main):153:0> x.length
=> 2
irb(main):154:0> x.offset 1
=> [0, 3]
irb(main):155:0> x.offset 0
=> [0, 3]