return next and pl/perl

Hi all,
    I'm working on implementing a function in PL/PERL that will ready
many rows.  As such I'd like to use return_next to keep memory usage
down.  When I call return next, I get the following error message:

ERROR:  error from Perl function: Can't call method "return_next" on
unblessed reference at (eval 18) line 25.

likewise if I use spi_return_next:
ERROR:  error from Perl function: Can't call method "spi_return_next" on
unblessed reference at (eval 16) line 25.

After some Google and list searching, I inferred that spi_return_next
may not be implemented?  Is this correct?  If so, is there a workaround?

Thanks,

Eric