[S04] small nit

let and temp are prefix operators, not ordinary functions

S04-control.pod

@@ -176,7 +176,7 @@ get separate state variables.  However, recursive calls to the same
 clone use the same state variable.
 
 Perl 5's "C<local>" function has been renamed to C<temp> to better
-reflect what it does.  There is also a C<let> function that sets a
+reflect what it does.  There is also a C<let> prefix operator that sets a
 hypothetical value.  It works exactly like C<temp>, except that the
 value will be restored only if the current block exits unsuccessfully.
 (See Definition of Success below for more.)  C<temp> and C<let> temporize