Address Victor's nits

Author: ambv

Doc/using/cmdline.rst

@@ -553,10 +553,11 @@ Miscellaneous options
      container system. See also :envvar:`PYTHON_CPU_COUNT`.
      If *n* is ``default``, nothing is overridden.
    * :samp:`-X presite={package.module}` specifies a module that should be
-     imported before ``site.py`` is executed and before the :mod:`__main__`
-     module exists.  Therefore, the imported module isn't :mod:`__main__`.
-     Python needs to be :ref:`built in debug mode <debug-build>` for this
-     option to exist.  See also :envvar:`PYTHON_PRESITE`.
+     imported before the :mod:`site` module is executed and before the
+     :mod:`__main__` module exists.  Therefore, the imported module isn't
+     :mod:`__main__`. This can be used to execute code early during Python
+     initialization. Python needs to be :ref:`built in debug mode <debug-build>`
+     for this option to exist.  See also :envvar:`PYTHON_PRESITE`.
 
    It also allows passing arbitrary values and retrieving them through the
    :data:`sys._xoptions` dictionary.
@@ -1113,9 +1114,14 @@ Debug-mode variables
 .. envvar:: PYTHON_PRESITE
 
    If this variable is set to a module, that module will be imported
-   early in the interpreter lifecycle, before ``site.py`` is executed,
-   and before the :mod:`__main__` module is created.  Therefore, the
-   imported module is not treated as :mod:`__main__`.
+   early in the interpreter lifecycle, before the :mod:`site` module is
+   executed, and before the :mod:`__main__` module is created.
+   Therefore, the imported module is not treated as :mod:`__main__`.
+
+   This can be used to execute code early during Python initialization.
+
+   To import a submodule, use ``package.module`` as the value, like in
+   an import statement.
 
    See also the :option:`-X presite <-X>` command-line option,
    which takes precedence over this variable.