my $ref_header = [ 'Name', 'Surname' ];
my @ref_db_data = @{ $sth->fetchall_arrayref };
unshift @ref_db_data, $ref_header;

##</code><code>##

my $ref_header = [ 'Name', 'Surname' ];
my $ref_db_data = $sth->fetchall_arrayref;
unshift @{ $ref_db_data }, $ref_header;

##</code><code>##

my @ref_header = ( 
       [ ["Name", "Surname"] ],
    );
...
@ref_db_data = $sth->fetchall_arrayref;
unshift @{$ref_db_data[0]}, $ref_header[0]->[0];

##</code><code>##

@ref_db_data = ( [ [ 'Name', 'Surname' ],
                   [ 'John', 'Doe'     ],
                   [ 'Jane', 'Smith'   ]
                 ]
               );