dws,
I thought this too and almost replied, but I got distracted. It would be good to point out that while you can change "set" the environment that you fork (child process), you can't export it back to the parent. I was guessing that the OP was trying to do the equivalent of:

$ perl -e 'cd /tmp'
$ pwd
 /home/user
$ echo "WTF?"
[download]

Cheers - L~R

Update: I can neither confirm nor deny it (without research anyway), but I heard this actually works on VMS. And while you can set the parent to read information from the child and set the parameters itself in the OS's I was originally referring to, the child is not actually doing it.