CREATE EXTENSION plperlu;

CREATE FUNCTION tied_setof_text() RETURNS SETOF text
LANGUAGE plperlu AS $$
  use Tie::Array;
  my @a;
  tie @a, 'Tie::StdArray';
  @a = ('p', 'q', 'r');
  return \@a;
$$;

SELECT * FROM tied_setof_text();