lt3luabridge

lt3luabridge is an expl3 package for plain TeX, LaTeX, and ConTeXt that allows you to execute Lua code in LuaTeX or any other TeX engine that exposes the shell:

\documentclass{standalone}
\usepackage{lt3luabridge}
\begin{document}
$ 1 + 2 = \luabridgeExecute{ print(1 + 2) } $
\end{document}

lt3luabridge was previously part of the Markdown package for TeX, where it has been battle-tested since 2016. Since 2022, lt3luabridge has been available as a separate package.