This simple package is designed to read a list of items whose
parsing character may be selected by the user. Once the list is
read, its items are stored in a structure that behaves as a
dimensioned array. As such, it becomes very easy to access an
item in the list by its number. For example, if the list is
stored in the macro \foo, the item #3 is designated by \foo[3].
A component may, in turn, be a list with a parsing delimiter
different from the parent list, paving the way for nesting and
employing a syntax reminiscent of an array of several
dimensions of the type \foo[3,2] to access the item #2 of the
list contained within the item #3 of the top-tier list.

Homepage:
https://ctan.org/pkg/listofitems
