var Closure
------------------------------------ SECURITY XXX: Closure and Closure2 below are exported package-level function-typed vars that any foreign realm can set via SetClosure / SetClosure2 and trigger via ExecuteClosure / ExecuteClosureCross. Closure2's signature is `func(realm)`, which means whoever sets it receives a realm value at invocation time — capability-bearing data stored in an exported package var, then handed back to caller-supplied code. THIS IS DELIBERATE VM-PARITY-TEST INFRASTRUCTURE — these vars exist to exercise the VM's handling of stored closures and cross- realm callbacks. DO NOT COPY THIS PATTERN IN PRODUCTION CODE. Real /r/ realms must never expose `func(realm)` (or any function-typed value capable of receiving cur) as an exported package var.