Dear Sir or Madam,
first of all: I don't have any experiences with fhem nor perl. But I am experienced with embedded hardware and software. I worked with bus-systems before, so it is possible to help you.
I will write down all steps we made, so you can reuse that work if necessary.
I suggest a remote connection to your PC and skype discussion to help you.
As a native speaker, german is no problem for me.
Vennlig hilsen, Stefan