So $rows_data is an arrayref? Shouldn't it be something like :

foreach( @{$rows_data} ){
    $sth2->execute($_);
    my $count = $sth2->fetchrow_array;
    push @$rows_data, { count => $count };
}
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Anyway, I'm still not clear of what this whole thing is doing. Could you post whole code snippet related to $rows_data ...