User blog comment:SuperSpruce/The T Array Function Part 5: Arbitrary Comma T Function (ACT)/@comment-36984051-20190628175028/@comment-35470197-20190628233216

> C. If a } is immediately before it, follow these steps. The initial array will be [#{@}$c%]. Note that the array can have any subscript.

As I pointed out in the comments to your previous blog post, expressiong an array into the expression of the form [#{@}$c%] is not unique because # and % can be any substrings. Therefore you need to define precisely the substring #, @, $, c, and %.