6. Functions

  The Rexx Summary contains a list of the functions which are available in
  Rexx.  Each of these functions performs a specific operation upon the
  parameters. For example,

      /* Invoke the date function with various parameters */
      say date("W")',' date()

  This might say, for example, "Friday, 22 May 1992".

  A function is called by typing its name immediately followed by "(".
  After that come the parameters, if any, and finally a closing ")". Note
  that you should not type a space between the name and "(", because that
  space would be a concatenation operator, as in section 4. In the above
  example, the "date" function is called twice.  The value of date("W") is
  the name of the weekday, and the value of date() is the date in "default"
  format.