Regex.Replace: How to use $groups followed by numbers [duplicate]

Question

With Regex::Replace we can use $1, $2, ... to match corresponding groups. But how can I use $1 followed by number. E.g. to replace 6 with 678?

 Regex::Replace(text, "(6)", '$178'); 

Answer 1

You need to use the alternate syntax:

Regex::Replace(text, "(6)", "${1}78"); 

Answer 2

It seems I can use $`

Regex::Replace(text, "(6)", '$1$`78');