DOC: update documentation _->.

src/doc/cfood.rst

@@ -183,8 +183,10 @@ Automatically generated keys
 
 Some variable names are automatically generated and can be used using the
 ``$<variable name>`` syntax. Those include:
+
 - ``<converter name>``: access the path of converter names to the current converter
-- ``<converter name>_path``: the file system path to the structure element
-  (file system related converters only)
+- ``<converter name>.path``: the file system path to the structure element
+  (file system related converters only; you need curly brackets to use them:
+  ``${<converter name>.path}``)
 - ``<Record key>``: all entities that are created in the ``records`` section
   are available under the same key