Tests fail above 5.26 when . is not in @INC

[toddr]

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02:39:09 27827 ERROR [463]: + ./Build test
02:39:09 27827 ERROR [463]: # Test 3 got: "0" (t/01-basic.t at line 15)
02:39:09 27827 ERROR [463]: #   Expected: ""
02:39:09 27827 ERROR [463]: #  t/01-basic.t line 15 is: ok $file1->is_absolute, '';
02:39:09 27827 ERROR [463]: # Test 7 got: "0" (t/01-basic.t at line 21)
02:39:09 27827 ERROR [463]: #   Expected: ""
02:39:09 27827 ERROR [463]: #  t/01-basic.t line 21 is: ok $file2->is_absolute, '';
02:39:09 27827 ERROR [463]: # Test 11 got: "0" (t/01-basic.t at line 27)
02:39:09 27827 ERROR [463]: #    Expected: ""
02:39:09 27827 ERROR [463]: #  t/01-basic.t line 27 is: ok $file3->is_absolute, '';
02:39:09 27827 ERROR [463]: # Test 16 got: "0" (t/01-basic.t at line 34)
02:39:09 27827 ERROR [463]: #    Expected: ""
02:39:09 27827 ERROR [463]: #  t/01-basic.t line 34 is: ok $dir->is_absolute, '';
02:39:09 27827 ERROR [463]: t/01-basic.t .......... 
02:39:09 27827 ERROR [463]: Failed 4/78 subtests 
02:39:09 27827 ERROR [463]: t/02-foreign.t ........ ok
02:39:09 27827 ERROR [463]: t/03-filesystem.t ..... ok
02:39:09 27827 ERROR [463]: t/04-subclass.t ....... ok
02:39:09 27827 ERROR [463]: t/05-traverse.t ....... ok
02:39:09 27827 ERROR [463]: t/06-traverse_filt.t .. ok
02:39:09 27827 ERROR [463]: t/07-recurseprune.t ... ok
02:39:09 27827 ERROR [463]: t/author-critic.t ..... skipped: these tests are for testing by the author
02:39:09 27827 ERROR [463]: 
02:39:09 27827 ERROR [463]: Test Summary Report
02:39:09 27827 ERROR [463]: -------------------
02:39:09 27827 ERROR [463]: t/01-basic.t        (Wstat: 0 Tests: 78 Failed: 4)
02:39:09 27827 ERROR [463]:   Failed tests:  3, 7, 11, 16
02:39:09 27827 ERROR [463]: Files=8, Tests=248,  1 wallclock secs ( 0.06 usr  0.02 sys +  0.52 cusr  0.07 csys =  0.67 CPU)
02:39:09 27827 ERROR [463]: Result: FAIL
02:39:09 27827 ERROR [463]: Failed 1/8 test programs. 4/248 subtests failed.

[toddr]

I've not dug deep here as I'm opening about 30 cases today. We built our set of modules with PERL_USE_UNSAFE_INC=1 and got the build working 100% then I set it to 0 and re-tried with the above failure. so either this is a flapping test or a test that makes assumptions about . in @INC.