Current stable doesn't configure w/ current stable bash.
All the latest unstable ebuilds are already bash-3.1 compatible. Just the stabilization is needed.
Which version should we test?
I think 2.0.0_rc6-r1 could be sufficient. If you have time, 1.9.9-r2 also, but it is not used very much.
Sorry that this took so long to get tested.