<type>PostgreSQL::InServer::ARRAY</type> object. This object may be treated as an array
   reference or a string, allowing for backward compatibility with Perl
   code written for <productname>PostgreSQL</productname> versions below 9.1 to
   run.  For example:

<programlisting>
CREATE OR REPLACE FUNCTION concat_array_elements(text[]) RETURNS TEXT AS $$
    my $arg = shift;
    my $result = "";
    return undef if (!defined $arg);

    # as an array reference
    for (@$arg) {
        $result .= $_;
    }

    # also works as a string
    $result .= $arg;

    return $result;
$$ LANGUAGE plperl;

SELECT concat_array_elements(ARRAY['PL','/','Perl']);
</programlisting>

  <note>
   <para>
    Multidimensional arrays are represented as references to
    lower-dimensional arrays of references in a way common to every Perl
    programmer.
   </para>
  </note>
  </para>

  <para>
   Composite-type arguments are passed to the function as references
   to hashes.  The keys of the hash are the attribute names of the
   composite type.  Here is an example:

<programlisting>
CREATE TABLE employee (
    name text,
    basesalary integer,
    bonus integer
);

CREATE FUNCTION empcomp(employee) RETURNS integer AS $$
    my ($emp) = @_;
    return $emp-&gt;{basesalary} + $emp-&gt;{bonus};
$$ LANGUAGE plperl;

SELECT name, empcomp(employee.*) FROM employee;
</programlisting>
  </para>

  <para>
   A PL/Perl function can return a composite-type result using the same
   approach: return a reference to a hash that has the required attributes.
   For example:

<programlisting>
CREATE TYPE testrowperl AS (f1 integer, f2 text, f3 text);

CREATE OR REPLACE FUNCTION perl_row() RETURNS testrowperl AS $$
    return {f2 =&gt; 'hello', f1 =&gt; 1, f3 =&gt; 'world'};
$$ LANGUAGE plperl;

SELECT * FROM perl_row();
</programlisting>

   Any columns in the declared result data type that are not present in the
   hash will be returned as null values.
  </para>

  <para>
   Similarly, output arguments of procedures can be returned as a hash
   reference:

<programlisting>
CREATE PROCEDURE perl_triple(INOUT a integer, INOUT b integer) AS $$
    my ($a, $b) = @_;
    return {a =&gt; $a * 3, b =&gt; $b * 3};
$$ LANGUAGE plperl;

CALL perl_triple(5, 10);
</programlisting>
  </para>

  <para>
    PL/Perl functions can also return sets of either scalar or
    composite types.  Usually you'll want to return rows one at a
    time, both to speed up startup time and to keep from queuing up
    the entire result set in memory.  You can do this with
    <function>return_next</function> as illustrated below.  Note that
    after the last <function>return_next</function>, you must put
    either <literal>return</literal> or (better) <literal>return
    undef</literal>.

<programlisting>
CREATE OR REPLACE FUNCTION perl_set_int(int)
RETURNS SETOF INTEGER AS $$
    foreach (0..$_[0]) {
        return_next($_);
    }
    return undef;
$$ LANGUAGE plperl;

SELECT * FROM perl_set_int(5);

CREATE OR REPLACE FUNCTION perl_set()
RETURNS SETOF testrowperl AS $$
    return_next({ f1 =&gt; 1, f2 =&gt; 'Hello', f3 =&gt; 'World' });
    return_next({ f1 =&gt; 2, f2 =&gt; 'Hello', f3 =&gt; 'PostgreSQL' });
    return_next({ f1 =&gt; 3, f2 =&gt; 'Hello', f3 =&gt; 'PL/Perl' });
    return undef;
$$ LANGUAGE plperl;
</programlisting>

    For small result sets, you can return a reference to an array that
    contains either scalars, references to arrays, or references to
    hashes for simple types, array types, and composite types,
    respectively.  Here are some simple examples of returning the entire
    result set as an array reference:

<programlisting>
CREATE OR REPLACE FUNCTION perl_set_int(int) RETURNS SETOF INTEGER AS $$
    return [0..$_[0]];
$$ LANGUAGE plperl;

SELECT * FROM perl_set_int(5);

CREATE OR REPLACE FUNCTION perl_set() RETURNS SETOF testrowperl AS $$
    return [
        { f1 =&gt; 1, f2 =&gt; 'Hello', f3 =&gt; 'World' },
        { f1 =&gt; 2, f2 =&gt; 'Hello', f3 =&gt;