Need help to search all dc's available

hi all,
I am trying to write one tool, that could find the all available dc
values.
see example:
-> base dn: dc=A, dc=B, dc=C
                  ou =users, dc=A, dc=B, dc=C
                  ou= groups,dc=A, dc=B, dc=C
                  dc=D, dc=A, dc=B, dc=C
                            ou=users, dc=D, dc=A, dc=B, dc=C
something like structure I have in LDAP DIR,
now I just want to find out all avalable dc's by accepting base dn as
input in PERL:LDAP.
How I can do that? any tutorial / script?

Thanks,
Omi