Some random Python project:

    proj/.autoenv.zsh:
        autostash PATH
        path=(~/local/stow/py310/bin $path)
        . ~w/pyderasn-venv/bin/activate
        export -TU PYTHONPATH pythonpath
        pythonpath=(. src $pythonpath)
    proj/.autoenv_leave.zsh:
        deactivate

Some random C project:

    proj/.autoenv.zsh:
        autostash LD_LIBRARY_PATH MANPATH
        ld_library_path=(~w/libressl/lib ~w/local/lib $ld_library_path)
        manpath=(~w/libressl/share/man $manpath)
        autostash NSPR_LOG_MODULES=all:5 SSLDEBUG=1 SSLTRACE=125