Redefine operator = for text

Hello All,

Is it possible to change the behavior of operator "=" for text? I
wolud like to redefine this operator in order to it compare strings
without checking of letter case.
I tried the following:

create function TextEqual(text, text)
returns bool
as '
begin
if texteq(upper($1), upper($2)) then
return TRUE;
else
return FALSE;
end if;
end;
'
language 'plpgsql';

drop operator = (text, text);
create operator = (
leftarg=text,
rightarg=text,
procedure=TextEqual,
commutator='=',
negator='<>',
restrict=eqsel,
join=eqjoinsel
);

This works, but after that many queries return error "unknown operator
98".

--
Best regards,
Yury mailto:yura(at)vpcit(dot)ru