For a brand new process, you should get 0, 1 and 2 assigned to standard input, standard output and standard error resp. (I know you *already* know this, but bear with me).

It's the shell that's responsible setting stdin, -out, and -err up. I know you can have more open when perl starts up if you explicitly request it (e.g. $ perl prog 3> extra-output). I assume there aren't any at-all-POSIX-y shells that open more fd's by default. Anyone know if that's true?

So, if you really want to start from 4 instead of 3 (I wonder why, but I'm sure you have a good reason)

I wanted to leave STDERR as fd 2, but I figured it'd be easier to remember that even-numbered fd's were input and odd-numbered fd's were output.