set-valued function difference in 8.1.0 vs 8.0.2

I just wanted to make sure this change in behavior is
a feature and not a bug.

This block of code with a (mis?)use of a set-valued function:

CREATE OR REPLACE FUNCTION foo() RETURNS SETOF varchar AS $$ {
my $res = [];
push @$res,'a';
push @$res,'b';
return $res;
} $$ LANGUAGE plperl STABLE;
select * from foo();
select foo();

worked "fine" in 8.0.2 but gives an

ERROR: set-valued function called in context that cannot accept a set

error in 8.1.0.

The 8.0.2 behavior of expanding the set-valued function when used
in the left part of the select clause was convenient in some
functions where I had used it like this:

select addr,geocode_alternatives(addr) from (
select addr from table where ambiguous=true
) as a;

where geocode_alternatives was a set-valued function that returned
all the alternatives for the ambiguous addresses.

Basically the results with 8.0.2 were something like:
addr | geocode_alternative
-----------+----------------
1 main st | 1 N main st
1 main st | 1 S main st
1 main st | 1 main ave
30 mlk dr | 2 Martin Luther King dr
30 mlk dr | 2 milk dr

And now I'm having a hard time coming up with a way of
re-writing it without a similar error. Is there an
easy way of rewriting this construct where the results
of a function can expand the result set that works
nicely in 8.1?

Thanks,
Ron