How can you truncate a string with commas in Ruby?

Question

ruby

There used to be a site rubydev.ru, and there was almost everything about ruby, but right now there is no such thing.
Here, for example, there is a line:
str='Область, город, улица'
How can you leave the text, cutting off the rest, which is up to the second comma, starting from the end ?
In our case, it should remain like this: str='city, street'

Answer 1

One of the options:
str.gsub(/^([а-яА-Я]+, )?/,'')