plperl.on_init - bug or just me?

From memory and the thread below, I thought one of the key uses was to
let me use a module from trusted plperl.
http://archives.postgresql.org/pgsql-hackers/2010-02/msg00167.php

The example below has a TestModule that just exports one sub - visible
from plerlu but not plperl. Presumably "Safe" just clamps down and my
sub isn't marked as acceptable. Is this intended, or am I doing
something stupid?

postgresql.conf:
plperl.on_init =
'use lib "/home/richardh/dev/"; use TestModule qw(add_one);'

-- tries to call TestModule::add_one
richardh=# SELECT add_one(1);
ERROR: Undefined subroutine &TestModule::add_one called at line 1.
CONTEXT: PL/Perl function "add_one"

-- tries to call the exported main::add_one
richardh=# SELECT add_one_e(1);
ERROR: Undefined subroutine &main::add_one called at line 1.
CONTEXT: PL/Perl function "add_one_e"

-- plperlu - TestModule::add_one
richardh=# SELECT add_one_u(1);
add_one_u
-----------
2
(1 row)

--
Richard Huxton
Archonet Ltd