Problem with function invocation

 Hello.

 When I create next function:

     create function pilpot() returns integer as '
        declare
            foo integer;
        begin
            foo = insert into aviso(user) values(1);
            return foo;
        end;
    ' language 'plpgsql';

 And try to invoque with:

     # select pilpot();

 I get next error:

     ERROR: parser: parse error at or near "("

 Where is the problem with this?

 Thanks a lot.

                                 David