Sorry if my tone offended. It's just that I've been burned enough times by hardware kludges, I tend to mount the soapbox when I see others toying with the same fate. Especially since you indicate it's not a one-off project, I still maintain it's worth the time to figure out what's going on and get it right.
I confess confusion now regarding the separation/non-separation of the RD and SEND lines. I'd be happy to provide more assistance if I knew more about the circuitry of your RS232 converter. Unfortunately, this goes outside the realm of Perl, so this probably isn't the best forum to continue the discussion. Perhaps you could message me on the Chatterbox with your email address, and we could continue there.