title: Replace '%@' with '%n$s' using groovy regex
body: <p>I have a string like <code>some text %@ some text %@ some text</code>
  where <code>%@</code> is a obj-c formatting. I need to transform this string to <code>some text %1$s some text %2$s some text</code> , which is a android resource with formatting.</p>
  
  <p>How can I do it using groovy regex?</p>