Here is my example demonstrating an advantage to merely operating through a reference.
I would find it to be much more tedious to do exactly the same thing on without a reference.

use Hash::Merge qw( merge );

sub getTop25{
    
    my ($dbh, $sth);
    $dbh = DBI->connect('DBI:ODBC:cdratelistingservice','$db','$psswd'
+); # ODBC connect
    unless ($dbh->ping) {
        print "Error opening database: $DBI::errstr\n";
        exit;
    } 
    my $connected = $dbh->ping;

    $dbh->{FetchHashKeyName}='NAME_lc';

    @fields = ( "30_day", "60_day", "90_day", "180_day", "270_day", "1
+_year", 
                "18_month", "2_year", "3_year", "4_year", "5_year", "v
+ariable_1", "variable_2", "variable_3" );
    my $num_fields;
    $num_fields = @fields;
    for (my $i=0;$i<$num_fields;$i++) {
        $sql = "Select TOP 25 $fields[$i], key from cdrates c, main m 
+WHERE r.key = m.key and m.valid = '$date' ORDER BY $fields[$i] DESC";
        push @sql, $sql;
    }
# @hashref demonstrates the advantage to merely 
# operating through a reference. 
    $num_queries = @sql;
    for (my $j=0;$j<$num_queries;$j++) {
# update to check whether or not the database queries are
# successful or not
        my $hashref = $dbh->selectall_hashref($sql[$j], "key") or die 
+$dbh->errstr; 
        push @hashref, $hashref;
    }
 # here i merge all hashes in order to display only
 # 1 instance of an institution that is posting a top25 
 # jumbo CD rate in any of the above catagories (fields)
    $num_hashref = @hashref;
    for (my $k=0;$k<$num_hashref;$k++) {
         %complex = %{ merge( \%complex, \%{$hashref[$k]} ) };
    } 

    my $num_merge=scalar(keys %complex);
    print "\n\t$num_merge RECORDS Found\n";
    
}

sub GetStationNumbers{

    my ($dbh, $sth);
    $dbh = DBI->connect('DBI:ODBC:poop'); # ODBC connect
    unless ($dbh->ping) {
        print "Error opening database: $DBI::errstr\n";
        exit;
    } else {
        #print "\n\nQuerying ACT! dBASE DB\n\n";
    }
    my $connected = $dbh->ping;

    $dbh->{FetchHashKeyName}='NAME_uc';

    my $sql;
    my @sql, @hashref;

    foreach my $key (sort keys %complex) {
        $sql = "SELECT station_number FROM inst where key = '$key'";
        push @sql, "$sql";
    }
    

    my $num_qeries;
    $num_queries = @sql;

    for (my $j=0;$j<$num_queries;$j++) {
#  update to check whether or not the database queries are
#  successful or not
        my $hashref = $dbh->selectall_hashref($sql[$j], "key") or die 
+$dbh->errstr;
        push @hashref, $hashref;
    }
    my $num_hashref;
    $num_hashref = @hashref;
    for (my $k=0;$k<$num_hashref;$k++) {

         %complex = %{merge( \%complex, \%{$hashref[$k]} )};
 # I use a reference here just because I felt like it.
         $HoH_ref = \%complex;
    } 
    
    my $num_merge=scalar(keys %complex);
}
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