my $foo;
my $foo_new;

sub fooz : lvalue
{
     $foo;
}

$foo = "Bar";      # Initialization
print fooz,"\n";   # Reading
fooz = "Foo";      # Assignment
print fooz,"\n";   # Reading

##</code><code>##

my $foo;
my $foo_new;

sub fooz : lvalue
{
     defined ($foo_new)?
        $foo_new
        : (islvalue?
              $foo_new = $foo
              : $foo);
}

$foo = "Bar";      # Initialization
print fooz,"\n";   # Reading
fooz = "Foo";      # Assignment
print fooz,"\n";   # Reading