Merge topic 'doc-ENVIRONMENT_MODIFICATION' into release-3.22

f6177f05da Help: Clarify ENVIRONMENT_MODIFICATION case sensitivity

Acked-by: Kitware Robot <[email protected]>
Reviewed-by: Ben Boeckel <[email protected]>
Merge-request: !6661

Help/prop_test/ENVIRONMENT_MODIFICATION.rst

@@ -8,8 +8,9 @@ that the operations performed by this property are performed after the
 :prop_test:`ENVIRONMENT` property is already applied.
 
 If set to a list of environment variables and values of the form
-``MYVAR=OP:VALUE``. Entries are considered in the order specified in the
-property's value. The ``OP`` may be one of:
+``MYVAR=OP:VALUE``, where ``MYVAR`` is the case-sensitive name of an
+environment variable to be modified. Entries are considered in the
+order specified in the property's value. The ``OP`` may be one of:
 
   - ``reset``: Reset to the unmodified value, ignoring all modifications to
     ``MYVAR`` prior to this entry. Note that this will reset the variable to