+Note that C<-s/a/b/> does not do a negated substitution. Saying
+C<-exp($foo)> still works as expected, however: only single letters
+following a minus are interpreted as file tests.
+
+These operators are exempt from the "looks like a function rule" described
+above. That is, an opening parenthesis after the operator does not affect
+how much of the following code constitutes the argument. Put the opening
+parentheses before the operator to separate it from code that follows (this
+applies only to operators with higher precedence than unary operators, of
+course):
+
+ -s($file) + 1024 # probably wrong; same as -s($file + 1024)
+ (-s $file) + 1024 # correct
+