sub TIESCALAR { bless \my $o => $_[0] }
sub STORE { $_[1] = "Touched by STORE\n" }
tie my $a => 'main';
my $b = "Untouched by STORE\n";
$a = $b;
print $b; # => Untouched by STORE
tied($a)->STORE($b);
print $b; # => Touched by STORE