More than 9 backreferences in gsub()

Question

How to use gsub with more than 9 backreferences? I would expect the output in the example below to be \"e, g, i, j, o\".

> test <- \"abcdefghijklmnop\"
&g         


        

Answer 1

It was my understanding that \10 would we understood as backreference 0 followed by a digit of 1. I think 9 is the max.