CREATE EXTENSION hstore_plperl CASCADE;
NOTICE:  installing required extension "hstore"
NOTICE:  installing required extension "plperl"
SELECT transforms.udt_schema, transforms.udt_name,
       routine_schema, routine_name,
       group_name, transform_type
FROM information_schema.transforms JOIN information_schema.routines
     USING (specific_catalog, specific_schema, specific_name)
ORDER BY 1, 2, 5, 6;
 udt_schema | udt_name | routine_schema |   routine_name   | group_name | transform_type 
------------+----------+----------------+------------------+------------+----------------
 public     | hstore   | public         | hstore_to_plperl | plperl     | FROM SQL
 public     | hstore   | public         | plperl_to_hstore | plperl     | TO SQL
(2 rows)

-- test perl -> hstore
CREATE FUNCTION test2() RETURNS hstore
LANGUAGE plperl
TRANSFORM FOR TYPE hstore
AS $$
$val = {a => 1, b => 'boo', c => undef};
return $val;
$$;
SELECT test2();
              test2              
---------------------------------
 "a"=>"1", "b"=>"boo", "c"=>NULL
(1 row)

-- test perl -> hstore[]
CREATE FUNCTION test2arr() RETURNS hstore[]
LANGUAGE plperl
TRANSFORM FOR TYPE hstore
AS $$
$val = [{a => 1, b => 'boo', c => undef}, {d => 2}];
return $val;
$$;
SELECT test2arr();
                           test2arr                           
--------------------------------------------------------------
 {"\"a\"=>\"1\", \"b\"=>\"boo\", \"c\"=>NULL","\"d\"=>\"2\""}
(1 row)

-- check error cases
CREATE OR REPLACE FUNCTION test2() RETURNS hstore
LANGUAGE plperl
TRANSFORM FOR TYPE hstore
AS $$
return 42;
$$;
SELECT test2();
ERROR:  cannot transform non-hash Perl value to hstore
CONTEXT:  PL/Perl function "test2"
CREATE OR REPLACE FUNCTION test2() RETURNS hstore
LANGUAGE plperl
TRANSFORM FOR TYPE hstore
AS $$
return [1, 2];
$$;
SELECT test2();
ERROR:  cannot transform non-hash Perl value to hstore
CONTEXT:  PL/Perl function "test2"
DROP FUNCTION test2();
DROP FUNCTION test2arr();
DROP EXTENSION hstore_plperl;
DROP EXTENSION hstore;
DROP EXTENSION plperl;