* backtracking positions remembered by any tokens inside the group.
* Example RegEx is `a(?>bc|b)c` if the given patterns are `abc` and `abcc` then
* `a(bc|b)c` matches both where as `a(?>bc|b)c` matches only abcc because
* backtracking positions remembered by any tokens inside the group.
* Example RegEx is `a(?>bc|b)c` if the given patterns are `abc` and `abcc` then
* `a(bc|b)c` matches both where as `a(?>bc|b)c` matches only abcc because