`t12.t` SEGV (linux/arm64?)

On some of my smoker systems (all of them are aarch64-linux systems) the test suite fails like this:
```
t/t12.t ................ 
No subtests run 
...
Test Summary Report
-------------------
t/t12.t              (Wstat: 139 (Signal: SEGV, dumped core) Tests: 0 Failed: 0)
  Non-zero wait status: 139
  Parse errors: No plan found in TAP output
```
