C -- Command name: symbol with interactive function definition.
d -- Value of point as number. Does not do I/O.
D -- Directory name.
-e -- Parametrized event (i.e., one that's a list) that invoked this command.
+e -- Parameterized event (i.e., one that's a list) that invoked this command.
If used more than once, the Nth `e' returns the Nth parameterized event.
This skips events that are integers or symbols.
f -- Existing file name.