while ( $rowref =  $sth->fetchrow_hashref() ) {push @data, %{$rowref};}

Without having tested yet, I think your problem is probably here*: You dereference $rowref before pushing it into the array, and a hash used in list context will return its key/value pairs:

my $hr1 = { foo=>'bar' };
my $hr2 = { quz=>'baz' };
my @data;
push @data, %{$hr1};
push @data, %{$hr2};
use Data::Dump;
dd @data;  # ("foo", "bar", "quz", "baz")
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Maybe you just want to push @data, $rowref; instead?

You might also be interested in DBI's fetchall_* methods?

* Update: Also here:

%row = $data[0]; ... foreach %row (@data)

These won't do what you expect. I think you want @data to be an array of hashes, which means that the elements of @data will contain references to hashes. You can't just assign a hashref to a hash^†, you need to either de-reference the hashref (e.g. my %hash = %{$hashref};, which is a bit expensive as it copies everything), or work with the hashref directly, e.g. $hashref->{key}.

I would strongly recommend having a look at perlreftut, perldsc, and perlref. Also, if you're not doing so already, Use strict and warnings!

^† Newer versions of Perl have an experimental feature called refaliasing.