You haven't included enough information for us to give you a proper answer. How does your shell script use this 'host_type' arguement? What does that have to do with FTP? I would say that if you can write your script without it, you don't need it. You seem to have checked the Net::FTP docs already. Without more information, that's all I can tell you.
Update: Host type is being set to IBM, UNIX, etc. I can't find any information on it anywhere, and I thought that it might be come sort of common switch in FTP that I was unaware of. Being unfamiliar with interfacing with UNIX, I thought that you had to tell UNIX what type of host is connecting in to it.
I don't know. I'll figure it out I suppose...or not.
Answering this question without knowing how HOST_TYPE and FTP relate didn't serve any positive purpose except to get me some knee-jerk --XP.:)
Seriously though, HOST TYPE is a common switch in FTP to specify the type of box that you are connecting to. I couldn't find this in Net_FTP as an option.
While assuming that if it's not in there, I don't need it, is interesting, it is incorrect. Sometimes you cannot view directory structures or complete operations without specifying HOST_TYPE in FTP.
More info on HOST TYPE is easy to find by searching the web. What I am interested in is how to specify it in Perl.