In general, it's the other way round you need to worry about more: perl on Windows lacks a number of functions that work on Unix (alarm, chroot, etc). However, the most important things to consider in making a script written on Windows work on Unix are when you interact with the system, either directly (using system or backticks), or indirectly (when manipulating files). Some general guidelines:
- Avoid system unless you want the user to have to install Unxutils or similar.
- Be careful with newlines: text files end in CRLF under Windows, but just LF under Unix.
- Use File::Spec, File::Temp and friends to construct paths and filenames portably.
- Know that unlink doesn't necessarily delete a file completely under Unix.
- Don't use Win32 modules, for obvious reasons.