- Split test suite out into separate files testing different bits.

- Get expectation count right in
    my @x = (1);
    my ($x, $y) = (@x, foo());

- Want::rvalues()

- Benchmark & optimise if necessary

- See what happens from FETCH/STORE routines (eek!)

- NUMBER, INTEGER (and STRING?) contexts. This will involve
  constructing a large and tedious table of ops indicating which
  args are treated as which sort of value.
