extradefs – A miscellany of support macros
The macros work equally in LaTeX and Plain TeX; no documentation is available, even as comments in the file.
Maybe you are interested in the following packages as well.
- declare: Declare register names locally
- miniltx: An abstract of LaTeX facilities for use with Plain TeX
- getoptk: Define macros with sophisticated options
- laps: Zero-width boxes for annotations, etc