I found that the trick is to tell pack to return utf8, thus:

Depending on what you want, the following tools are probably more appropriate:

• utf8::decode will decode UTF-8 into characters.
• utf8::upgrade will turn convert the internal representation to UTF-8. The behaviour of a few tools (such as uc and /\w/) varies based on the internal encoding.

Both are documented in utf8, but it's not necessary to do use utf8;. In fact, that means something different.