OT serial device "building blocks"

[Don Russell]

I have googled for this but am not finding anything suitable...

I have an old modem (actually  modem component with a serial interface) 
that I want to use to monitor an analog phone line.

I was hoping I could find some code like a "black box" that I can send 
commands (AT...) to, and it would give me the responses, and any 
asynchronous mesages, such as the RING message etc.

Part of the problem is this little gizmo sends some data as ascii 
characters, other data is sent as binary. (FSK data for things like the 
caller id info, VMWI etc.)

I would like to use Perl, or C, but was hoping I wouldn't have to 
re-invent the wheel to do the basic serial communications?

Does anybody have any suggestions, or good serial comms references you 
can point me to?

Thanks,
Don