LaTeX: package extract abuses internal LaTeX interfaces and seems to be highly incompatible with modern versions of LaTeX

Heads up:

The LaTeX package extract, used in the draft document, seems to intrude into private parts of the implementation of LaTeX, with high potential of breaking stuff. Compiling std.pdf emits nasty warnings at the end of the process:

(\end occurred inside a group at level 1)

### semi simple group (level 1) entered at line 86 (\begingroup)
### bottom level 

Latexmk marks these warnings as "very important" (it might have been some different but equivalent wording, not sure).

See https://tex.stackexchange.com/questions/605890/extract-package-causes-unfinished-group

the package redefines \begin and \end and completly breaks the new hook system of LaTeX, I wouldn't use it.

Write the author. He probably can use the new hooks instead of destroying them, or he could ask for real interfaces instead of redefining internal commands.

extract was created in 2005, long before any hook system was even discussed. So the new LaTeX destroyed the extract package.

Start by compiling std.pdf and reviewing the warnings attributed to the LaTeX package extract, then read the linked TeX Stack Exchange discussion about its redefinitions of \begin and \end. Done should mean the draft compiles without the unfinished-group warnings and remains compatible with modern LaTeX hooks, but the issue does not specify the implementation path.