If you go to search.cpan.org and look for 'serial', you should be able to find a module or two for the linux/bsd/*nix series of OSes. I believe there is also a Win32::Serial module or something similar.
In the case of the non-Win32 world, make sure that you have permission to read/write from /dev/ttyS0 or /dev/ttyS1 (or whichever serial port you're using).
Hope that helps.