perl-Plack-Middleware-Deflater-0.12-28.fc40 fails to build in Fedora 40 because all tests fail like this:

#   Failed test at t/content_type.t line 23.
#          got: undef
#     expected: 'Hello World'
#   Failed test at t/content_type.t line 38.
#          got: undef
#     expected: 'Hello World'
# Looks like you failed 2 tests of 6.
t/content_type.t .... 
Dubious, test returned 2 (wstat 512, 0x200)
Failed 2/6 subtests 

A difference between passing and failing build roots is at <https://koschei.fedoraproject.org/build/16236923>.