See the current Perl documentation for chroot.
Here is our local, out-dated (pre-5.6) version:
chroot - make directory new root for path lookups
This function works like the system call by the same name: it makes the
named directory the new root directory for all further pathnames that begin
"/" by your process and all its children. (It doesn't change your current working directory, which is unaffected.) For security reasons, this call is restricted to the superuser. If
FILENAME is omitted, does a