No one has mentioned cygwin yet, so I'll throw it out. If you have to option to install it on the target machines, that may cover the Unix commands that have no Windoze equivalent.

However, as implied by other responses, anything outside of pure Perl may have issues. For instance, the ps command comes in many flavors, and it's not always easy to tell which flavor(s) is(are) available at runtime by inspecting pathnames or even man pages.

If you can list your dependencies outside of Perl, you'll be halfway to porting it. You should also look at perlport and other resources for future programs.