software estimation

I have a piece of code written to copy files, and a lot more, to a mainframe. I have to write another piece of code, from scratch, to do the same of actions to the same set to a UNIX box. I have to estimate how long it will take to write the second piece using the first piece as my starting block. Does anyone know of any methodologies which I can say, given x lines of code, it may take me n hours? The target language is PERL, but I could substitute C/C++ at a pinch.

[quote]I have a piece of code written to copy files, and a lot more[/quote]
What are you copying that's not files?