To be more specific, I need to determine if a modem, used for dial-up has a connection established or not.

I'll here assume that you know (or are able to determine) that there is a modem connected to the serial port. If so, this is probably not a Perl problem, but more of a modem problem.

If this is a "Hayes-compatible" modem, you'll need to read the users manual for the modem in question to determine what 'AT' commands are supported by the modem. You'll have to find out if there is any AT command that will tell you what you want to know.

"Livet är hårt" sa bonden.
"Grymt" sa grisen...