I assume Devel:TraceUse is placing that code ref in @INC. If so, I'm guessing Devel::TraceUse needs to be loaded after all modifications to @INC have been made. If so, the first snippet below will exhibit the problem, but not the latter.

perl -d:TraceUse -Mlib=my-lib -e'use Fcntl'
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and

perl -Mlib=my-lib -d:TraceUse -e'use Fcntl'
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I can't verify this because the module fails its tests.