Sorry, I posted my reply too hastily. The second parameter you pass to ->selectall_arrayref must be a hash with the key Slice, not Columns:

my $data_all =  $connection->selectall_arrayref($query, { Slice => {} 
+} );
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Then, each element of $data_all will be a hashref (not a hash as you assume):

  my $currec = $row;
  foreach my $columns (keys %$currec){
    say $columns;
    say $currec{$columns};
  }
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Whenever you're in doubt about a data structure, consider using Data::Dumper to print it:

use Data::Dumper;
say Dumper $row;
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Then, each element of $data_all will be a hashref (not a hash as you assume)

Thank you so much! This was killing me! And a big duh on my assumption error.

I love that there's still a place on the internet where people can get helped, without being scolded (for their own errors, or judgement answers like "why do you want to do that?" Am old enough to miss newsgroup forums for help.

Thank you again.