Extract time and compare dates

Question

I would like to know if hh:mm:ss have following value : "00:00:00" but I can't extract those values from the date. I'm not interested in dd/mm/yy but they are included in the string I receive.
set serveroutput on;
declare
str varchar2(30);
dat date;
begin
str := '19/01/2008 00:00:00';
dat := to_date(pepe,'HH24:MI:SS'); -- can't do this because mask do not fit with input string
if dat = '00:00:00' then ....

Answer 1

Sorry there was a copypaste error. This is the problem:
set serveroutput on;
declare
str varchar2(30);
dat date;
begin
str := '19/01/2008 00:00:00';
dat := to_date(str,'HH24:MI:SS'); -- can't do this because mask do not fit with input string
if dat = '00:00:00' then ...
I only want to know how can I detect that hh:mm:ss, coming from a varchar, is equal to "00:00:00".