Version 2.83.0 (April 29, 2019)
  - Unix: Added a syntax-file for the nano-editor;
    contributed by Stephan Muesse
  - Made parentheses around condition in while and until optional
  - Better error messages on misaligned control structures
  - New functions external() and external$() to invoke functions
    from external c-libraries
  - Fixes for line-numbers in error messages
  - Revised and updated the documentation
