This command enables you to derive new user-defined commands from existing commands. User-defined commands accept arguments separated by whitespace. You can use the arguments in expressions by using $arg0...$argn, for example:

print 4+$arg0      # add 4 to the first argument and print result

define cmd
   ...
end

# Define add-args command to print sum of first 3 arguments
define add-args
    print $arg0+$arg1+$arg2
end