This algorithm suffers from the same issue that LanX pointed out.

The following data defeats the de-dup:

my $null = qq{\x00};
my @test_data = (
   { "a${null}1${null}b"=>"2" },
    { a => 1, b => 2}
);
[download]

My second program gives the correct results, although it too could be defeated by sufficiently crafted data.