my $x = 1;
sub foo { $x }

##</code><code>##

$MAIN_X  ---
            \
             -> +---+
$FOO_X  ------> | 1 |
                +---+

##</code><code>##

                +---+
$MAIN_X  -----> | 9 |
                +---+
              
                +---+
$FOO_X  ------> | 1 |
                +---+