an argument to defined() or undef(). Nor is it optional when you
want to do an indirect subroutine call with a subroutine name or
reference using the C<&$subref()> or C<&{$subref}()> constructs,
-although the C<$subref-E<gt>()> notation solves that problem.
+although the C<< $subref->() >> notation solves that problem.
See L<perlref> for more about all that.
Subroutines may be called recursively. If a subroutine is called
subroutine, then it behaves like an old-fashioned subroutine. It
naturally falls out from this rule that prototypes have no influence
on subroutine references like C<\&foo> or on indirect subroutine
-calls like C<&{$subref}> or C<$subref-E<gt>()>.
+calls like C<&{$subref}> or C<< $subref->() >>.
Method calls are not influenced by prototypes either, because the
function to be called is indeterminate at compile time, since