Oracle, how to pass a '&' in url and other special characters

Function to normalize url link, substitute special characters in link:

CREATE OR REPLACE FUNCTION urlencode( p_str in varchar2 ) return varchar2

AS

    l_tmp varchar2(12000);

    l_len number default length(p_str);

    l_bad varchar2(100) default ' >%}\~];?@&<#{|^[`/:=$+''"' || chr(10);

    l_char char(1);

BEGIN

    IF ( p_str is NULL ) then

        RETURN NULL;

    END IF;

    FOR i IN 1 .. l_len LOOP

        l_char := substr(p_str,i,1);

        IF ( instr( l_bad, l_char ) > 0 )

        THEN

            l_tmp := l_tmp || '%' || to_char(ascii(l_char), 'fm0X');

        ELSE

            l_tmp := l_tmp || l_char;

        END IF;

    END LOOP;

RETURN l_tmp;

END;

Example:

SET SERVEROUTPUT ON

DECLARE

link varchar2(2000) :=  'https://mail.google.com/mail/u/1/#inbox/FMfcgxwBVMgHsGkcMPpbLJFxMgkDmNNz&^';

linkencoded varchar2(2000);

BEGIN

linkencoded := urlencode(link);

DBMS_OUTPUT.PUT_LINE (linkencoded);

END;