Thank you andy for the suggestions!
This approach can be considered an offline one...I was looking for an online approach ( a sort of interception of add mod del and then an action related to that).
Furthermore, I would want to dig into this new backend to understand the potentiality.
However I am still stuck on how to mantain the state of ldap avoiding full sync in case of shutting down and crash.
And if someone have a good example of a working perl backend (SampleLdap it's just a skeleton).
Thank you again!
If all you want to do is trigger based on add/del/mod, May I suggest you take a look at the auditlog overlay? It will let you store changes in LDIF format to a file, which you could later parse very easily with something like Perl.
--andy