Texapi provides utility macros to write format-independent (and -aware) packages. It is similar in spirit to the etoolbox, except that it isn’t tied to LaTeX.

Tools include: engine and format detection, expansion control, command definition and manipulation, various testing macros, string operations, and highly customizable while and for loops.

The package requires e-TeX (and, should you want to compile its documentation, the pitex package is also needed).