Pattern Recursion in more detail

• Pattern recursion allows us to treat the contents of a particular pattern buffer as an independent subexpression

• (?1) recurses into the first capture buffer in the pattern

• (?R) and its alias (?0) allows us to treat the entire pattern as an independent subexpression

• If we have named a buffer we can also recurse into it by name by using (?&NAME)

• This is useful for writing grammars...