2526
2527
2528 - finally def :case supports quoted params

The cost: 40% slowdown in running all tests.

The contortions in getting at the right caller_scope suggest the
drawback of wart's approach compared to Kernel's. A $vau here would
simply bind a unique variable with the right caller scope.
2529 - optimization: support quoting only when needed

Now overhead is just 5% compared to 2527.