pl/pgsql or control structures outside of a function?

Hi all,

Is there any way to use PL/pgSQL code outside of a function?

The reason I'm asking is that I'm porting some code from
sybase/isql/SQR, and it allows some control code structures to be used
in an sql script. For instance,

begin
if ((select count(*) from users where login = 'foo') = 0)
begin
print 'Login "foo" does not exist.'
end
else
begin
print 'Adding account for "foo".'
insert into accounts values ('foo', 'bar')
end
end

PL/pgSQL looks like it would make this port rather easy, but all the
docs and examples I found never had an example of PL/pgSQL outside of
a function. For the purposes of this port I'd really prefer not to
create functions for all this. I searched through the PL/pgSQL docs
and even several Google searches but couldn't find a definitive
answer. It's fine if the answer is no, I'm just curious if I should
pursue this path or look for a different one. And if there's a way to
do this or something like it besides "create scripts in
Perl/Python/etc." that you know of, I'd appreciate any information.

Thanks,
Peter