BUG #6645: Getting an error with “ERROR: PL/Perl function must return reference to hash or array”?

The following bug has been logged on the website:

Bug reference:      6645
Logged by:          Evna Carroll
Email address:      me@evancarroll.com
PostgreSQL version: 9.1.2
Operating system:   Linux
Description:

This is a cross post from dba.stackexchange.com:
http://dba.stackexchange.com/q/17998/2639

The follow code used to work in Postgresql 8.4.11 with perl v5.10.1:

=# select * From testfunction();
      testfunction
------------------------
 http://www.google.com/
However, after doing a dump and load into Postgresql 9.1.3 with perl v5.14.2
I get:

ERROR:  PL/Perl function must return reference to hash or array
CONTEXT:  PL/Perl function "testfunction"
For reference, here is the function:

CREATE OR REPLACE FUNCTION testfunction(OUT text) AS $$
  use URI;
  return URI->new('http://www.google.com/')->canonical;
$$ LANGUAGE plperlu;
Again, the version of perl changed from v5.10.1 to v5.14.2; however, the
return from Data::Peek is the same across both versions:

$ perl -MData::Peek -MURI -e'DPeek(
    URI->new(q[http://www.google.com])->canonical
);'
Output on both versions of perl:

\PVMG("http://www.google.com/"\0)