[perl #126490] [BUG] Control exception handling is inconsistent and broken across backends. (SEGV on moar, CX unrecognized on jvm)

[Christian Bartolomaeus via RT]

As a status update: This code no longer segfaults on Moar:

$ perl6-m -e 'A: for 1 { for 1 { last A }; CONTROL { when CX::Last { say "last" 
}; default { .perl.say } } }'
chars requires a concrete string, but got null
  in block  at -e:1
  in block  at -e:1
  in block <unit> at -e:1