If you want to get, say, the value of "subject1" of each sequence, the easiest way is with the values keyword, as in:

my $data = $json->decode($jsonfeed);

my @values = ();

foreach my $value ( values %{ $data } ) {
    push(@values, $value->{'subject1'});
}

print Dumper( \@values );
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Which returns

$VAR1 = [
          'value',
          'value',
          'value'
        ];
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I'm not too clear on what values you're looking for, so I hope this helps.