This is a FAQ:

perldoc -q directory

I {changed directory, modified my environment} in a perl script. How come the change disappeared when I exited the script? How do I get my changes to be visible?

In the strictest sense, it can't be done--the script executes as a different process from the shell it was started from. Changes to a process are not reflected in its parent--only in any children created after the change. There is shell magic that may allow you to fake it by eval()ing the script's output in your shell; check out the comp.unix.questions FAQ for details.

In principle, changing the enclosing shell is workable, if your program outputs a new shell script, which the enclosing shell executes:

#!/usr/bin/ksh
echo "Doing what the Perl script tells me"
$(perl-script.pl)
[download]

#!/usr/bin/perl -w
print 'cd ~';
[download]