rlm_perl and checksimul

[d tbsky]

hi:
    I am using freeradius 3.0.4 comes with rhel 7.1.
I want to write a checksimul perl script. but it seems won't be called.
I create a rlm_perl instance "check_login", and put it under "default" site:

session {
        check_login
}

and at  perl script I write my code at finction below:

sub checksimul {
        &radiusd::radlog(L_INFO, "check_login: I am here");
        return RLM_MODULE_OK;
}

but "radiusd -X" show my code is not be called after user authentication.
the code works fine if I put it at "authroize" or "post-auth" section.
I don't know if I miss some steps or I met a bug..