Overloading '<' operator

Hi all,
 I was trying to overload '<' operator for (varchar,varchar). But  in
the function which handles the comparision I want to use the previous
'<' operator.. but it is going into a recursion.

My simplified code looks like :

create or replace function orastringcmp (varchar, varchar) returns
boolean as
'declare
        firstarg        alias for $1;
        secondarg       alias for $2;
begin
        return firstarg < secondarg;
end;
'language 'plpgsql';

create operator < (
        procedure = orastringcmp,
        leftarg = varchar,
        rightarg = varchar
);

Can any one tell how to use the previous version of ooperator while
overloading one. Are there any material online which gives the
detailed description of operator overloading? ( i could not find much
information apart from CREATE OPERATOR documentation )

Thanks,
Abhiman