__END__
# NAME calling undef sub belonging to undef GV
   my $foosub = \&foo;
   undef *foo;
   &$foosub;
EXPECT
Undefined subroutine &main::foo called at - line 3.
########
# NAME calling undef sub resident in its GV
   my $foosub = \&foo;
   &$foosub;
EXPECT
Undefined subroutine &main::foo called at - line 2.
########
# NAME calling undef scalar
   &{+undef};
EXPECT
Can't use an undefined value as a subroutine reference at - line 1.
########
# NAME calling undef magical scalar
   sub TIESCALAR {bless[]}
   sub FETCH {}
   tie $tied, "";
   &$tied;
EXPECT
Can't use an undefined value as a subroutine reference at - line 4.
