Shrubbery syntax for Racket(download.racket-lang.org)

Shrubbery notation is a set of text-level conventions that build toward a
full programming language, such as
Rhombus.
The notation is line- and indentation-sensitive, and it is intended to partially group
input, but leave further parsing to another layer, especially
enforestation.
The parsed form of a shrubbery imposes grouping to ensure that further
parsing is consistent with the shrubbery’s lines and indentation.

      1.4 Parentheses, Brackets, Braces, and Quotes

        2.1.2 Grouping by Opener–Closer Pairs

        2.1.3 Blocking with : and Indentation

        2.1.4 Continuing with Indentation and an Operator

        2.1.6 Separating Groups with ; and ,

        2.1.7 Line- and Column-Insensitivity with « and »

      5.2 Source Locations and Raw-Text Properties

      5.3 Reconstructing Shrubbery Notation