Slightly clarify explanation of WITH-ERRNO-HANDLER*.

doc/scsh-manual/syscalls.tex

@@ -49,7 +49,7 @@ Programs can use \ex{with-errno-handler*} to establish
 handlers for these exceptions.
 
 If a {\Unix} error arises while \var{thunk} is executing, 
-\var{handler} is called on two arguments:
+\var{handler} is called on two arguments like this:
         \codex{(\var{handler} \var{errno} \var{packet})}
 \var{packet} is a list of the form
      $$\var{packet} = \ex{(\var{errno-msg} \var{syscall} . \var{data})},$$