This is caused by a Parrot bug introduced in r36165, and resolved in
r36340. The example you gave exactly matches the reduced form of the
problem that I arrived at, before I traced the problem out of Rakudo and
into Parrot. See TT#256 at https://trac.parrot.org/parrot/ticket/256 .
If you cannot update your copy of Parrot to HEAD, then you can just
apply the single line patch that resolves the problem. To get the patch,
use `svn diff -c 36340 src/pmc/resizablestringarray.pmc`. The rest of
r36340 is the regression test for the bug.
