VSCode regex find & replace submatch math?
Given a regular expression of (foobar) you can reference the first group using $1 and so on if you have more groups in the replace input field.
To augment Benjamin's answer with an example:
Find Carrots(With)Dip(Are)Yummy
Replace Bananas$1Mustard$2Gross
Result BananasWithMustardAreGross
Anything in the parentheses can be a regular expression.