You want to emulate the interface of Net::FTP but you can't use Net::FTP?! It is part of the core - you don't even need to use CPAN.

Unless this is a school project or an educational exercie, this seems like a lot of reinventing the wheel. If you really, really have a good reason, then you might try studying the source code to get a better idea of how it is done. All of the source code is available via CPAN.

Quite honestly, if this is not a learning project and you need help figuring out how to do this, you are likely in way over your head with the project. If it is a learning project, it is very important that you define your scope and use cases very carefully before you begin, otherwise you will never reach the end.

When you study that module you will quickly see that there is a lot of complex code supporting that module. Code and documentation for that module alone is about 1800 lines. If your "can't use" rule extends further to its prerequesites (e.g. IO::Socket) the number of lines jumps up dramatically.

Even a guru programmer isn't going to write and thouroughly test that in less than a week. Assuming 1000 of that is lines of code, COCOMO 81 would put the time estimate at 3 months full time work! (that's for a single person of average skill).