add_action - bind a command verb to a local function

void add_action( string | function fun, string | string array cmd );

void add_action( string | function fun, string | string array cmd, int flag );

This efun is only available if NO_ADD_ACTION isn't defined.

Set up a function 'fun' to be called the a user types the command 'cmd'.
(What is the command is determined by the first 'word' which consists
of all the characters before the first space, with the exception of
verbs that don't need a space; see below).

If 'cmd' is an array, then that function will be called for any of the
commands in the array.  'fun' can either be a string which is the name
of a function in the object adding the command, or a function pointer.

Functions called by a user command will get the rest of the command line
as a string. It must then return 0 if it was the wrong command, otherwise 1.
If 1 is returned, no further parsing is done; if 0 is returned, other
commands will be checked (possibly the same command added by a different
object).  If no command is found, the default error message will be sent
to the player (traditionally, 'What?' but see also notify_fail())

For functions which can be called by more than one command, check query_verb()
to see which command was used.

Note: add_action() does not add commands globally; it only adds commands to
this_user(), and the object must be 'close' to the user it is adding commands
to.

Usually add_action() is called only from an init() routine. The object that
defines commands must be 'close' to the user, either being the user,
being carried by the user, being the room around the user, or being an
object in the same room as the user.

Since init() is called when a user moves 'close' to an object, it is a
convenient time to add such commands.  The commands are removed when the
user moves out of range (or the object does).

If argument 'flag' is 1, then only the leading characters of the command has
to match the verb 'cmd' and the entire verb is returned by query_verb().  If 
argument 'flag' is 2, then again, only the leading characters must match,
but query_verb() will only return the characters following 'cmd'.

See also:
 query_verb,
 remove_action,
 init