Test::Simple 0.81_02 has:

Test::Simple 0.81_02 has:
  Features Changed
     - Now preserves the tests' exit code if it exits abnormally,
       rather than setting it to 255.

$! is non-zero with PERLIO=stdio in some cases, so die would have set
the exit code to $! (typically 9). Now that would show through, so
ensure $! *is* zero to make sure that the exit code is 255.

p4raw-id: //depot/perl@34545