Looks like a bug... can reproduce something similar on Perl v5.10.1, not v5.20.0 via:

$ perl -MData::Dump=pp -e 'sub x {my %x=(A=>1,B=>2,B=>3)}; pp {x()}'
{ "" => "B", "B" => undef }

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In reply to Re: Missing Hash Keys When Hash Created in Sub by Anonymous Monk
in thread Missing Hash Keys When Hash Created in Sub by Stringer

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