CREATE OR REPLACE FUNCTION test(TEXT) RETURNS bool language plperl as $$
return (shift =~ /[a-z\u0105\u0107\u0119\u0142\u0144ó\u015b\u017a\u017c\u0104\u0106\u0118\u0141\u0143\u015aÓ\u0179\u017b0-9_-]+/i) || 0;
$$;
CREATE FUNCTION
select test('depesz');
 test 
------
 t
(1 row)

select test('depesz\u0105\u0107\u0119\u0142');
 test 
------
 t
(1 row)

select test('depesz\u0105\u0107\u0119\u0142$');
 test 
------
 t
(1 row)

select test('dePEsz\u0105\u0106\u0119\u0142$');
 test 
------
 t
(1 row)