bind_columns is binding columns ;), seriously though: NAME_lc are the lower case column names from the database, region and sales in this case, and these are in an array ref which is used as the keys for %row (using a hash slice). The reason it uses bind_columns is that it processes the columns one by one (allowing you to have a normal hash not a hash of an array). So it's doing something like this:

  $sth->bind_columns( \( @row{ @{$sth->{NAME_lc} } } ));
  # NAME_lc = lower case column name
  #    so it's equal to \@row{\@region} (and \@row{\@sales})
  # binds \$row{region} much as it would \$region
  while($sth->fetch)
  {
    # sets $row{region} with region's data
    # does same with sales
    print "$row{region}, $row{sales}\n";
    # since this is rebinded each time %row is overwritten
  }
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I hope this helps