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Commands are a special class of functions that only accept string input arguments. A command can be called as an ordinary function, but it can also be called without the parentheses. For example,
my_command hello world
is equivalent to
     my_command("hello", "world")
   The general form of a command call is
cmdname arg1 arg2 ...
which translates directly to
     cmdname ("arg1", "arg2", ...)
   Any regular function can be used as a command if it accepts string input arguments. For example:
     toupper lower_case_arg
        ⇒ ans = LOWER_CASE_ARG
   One difficulty of commands occurs when one of the string input arguments is stored in a variable. Because Octave can't tell the difference between a variable name and an ordinary string, it is not possible to pass a variable as input to a command. In such a situation a command must be called as a function. For example:
     strvar = "hello world";
     toupper strvar
        ⇒ ans = STRVAR
     toupper (strvar)
        ⇒ ans = HELLO WORLD