String value semantics?

[Luke Palmer]

Is this supposed to happen?

    % parrot -
    .sub _main
        $S0 = "Hello\n"
        $S1 = $S0
        substr $S1, 2, 2, ""
        print $S0
        print $S1
        end
    .end
    (EOF)
    Heo
    Heo

Aren't strings supposed to follow value semantics?

Luke