I have made various contacts with people inside Google, and it seems that the core App Engine team is busy with plenty of other things. However, this does not stop the community from getting something started. We will likely attract perl advocates within Google as we go along, even if they are not on the App Engine team. I would like to see the effort advance until the point where it becomes a simple matter for the App Engine team to embrace Perl.
I have started a project for all people interested in following this effort or contributing toward it.
Just as an update, Brad Fitzpatrick seems to be working on Perl on AppEngine. It seems that Google wants/needs to create a hardened/Safe/crippled version of Perl that is statically linked and can't load XS modules, which might take some time/effort. On the upside, Postgres already seems to have such an embedded Perl interpreter, so it might be not too much work to create a comparable embeddable static Perl.
Brad and Artur Bergman have pushed out Sys::Protect, which disables some Perl opcodes, which looks like a first step to disallowing system interaction.