R4RS 6.10  (call-with-input-file string procedure^1)   ==>  object
           (call-with-output-file string procedure^1)  ==>  object

PROCEDURE^1 should be a procedure of one argument, and STRING should
be a string naming a file. For CALL-WITH-INPUT-FILE, the file must
already exist; for CALL-WITH-OUTPUT-FILE, the effect is unspecified
if the file already exists. These procedures call PROCEDURE^1 with
one argument: the port obtained by opening the named file for input
or output.  If the file cannot be opened, an error is signalled.
If the procedure returns, then the port is closed automatically and
the value yielded by the procedure is returned. If the procedure
does not return, then the port will not be closed automatically
unless it is possible to prove that the port will never again be
used for a read or write operation.

S9fES silently overwrites the existing file when the file specified
in STRING already exists.
