I just looked over Device::Modem's page. Are you having difficulty because of the documentation? It took me a few read-throughs, but it appears to me that you want to use the atsend() function to send data to the modem, and answer() to receive it. (I think the atsend method is misnamed--it looks as if it should be just send. As it's named now, it appears that it's useful only for sending AT commands.) Does that help? (I hope so, as none of my computers has a modem connected to it...)

--roboticus