$self->sis->add_event("event name");
$self->sis->log_event("message");
$self->sis->uuid();

sub sis {
    return Company::Dept->new($dbh, $uname);
}
[download]

Every time you call a method on $self->sis you're going to construct a new instance of Company::Dept, which means you might as well not bother constructing instances at all, since you'll never retrieve any instance data.

I don't fully understand what $self is in the top three statements, but here's a way to have $self->sis persist from one statement to the next:

sub sis {
    my ($self) = @_;
    
    # check whether the internal representation is already defined
    if ( !$self->{_sis} ) {
        # call the constructor and save the result
        my ($dbh, $uname) = get_constructor_args_from_somewhere();
        $self->{_sis} = Company::Dept->new($dbh, $name);
    }

    return $self->{_sis};
}
[download]