$rboo = sub{($a,$b)=boo()};
$rzoo = sub{($a,$b)=zoo()};
$rhoo = sub{($a,$b)=hoo()};

print "return boo ", &$rboo, "\n" if (&$rboo);
print "return zoo ", &$rzoo, "\n" if (&$rzoo);
print "return hoo ", &$rhoo, "\n" if (&$rhoo);

sub boo {
  return (1, 'bar');
}

sub zoo {
  return (1, undef);
}

sub hoo {
  return 0;
}