From the report:
Test Summary Report
-------------------
t/t99thread.t (Wstat: 65280 Tests: 11 Failed: 0)
Non-zero exit status: 255
Parse errors: Tests out of sequence. Found (9) but expected (10)
Tests out of sequence. Found (10) but expected (11)
From
https://github.com/schwern/test-more/issues/labels/Test-Builder2#issue/100
threads are hosed in Test::Builder. The issue hasn't been fully
investigated.
Largely it should come down to making the event watchers fully shared
and having the EventCoordinator lock them when posting.
So skipping the threads tests on 2.00_anything.