-handle, you can write your own parser. But before you start, you
-should know a few things.
+handle, you can write your own <<xtypes:,extended type>>
+and use <<def_CF_XTYPE,`CF_XTYPE`>> macro to declare a new option.
+
+There is also an obsolete way to write a custom parser.
+Before you start, you should know a few things.