Actually, it appears that "/opt/..." is intended to be an absolute path for job that is being passed to "exec", in which case, based on looking at the error reports, the initial dot should probably not be there at all -- the exec call seems to be treating "<dot><space>/opt/..." as an actual path name, which obviously cannot exist.

update: Also, I think sauoq is quite right: if the "setup_env" file being exec'd is just going to exit after making its various environment settings, those settings will disappear when it exits, having no effect on the shell that ran this perl script.

Your only recourse for switching environment settings is to know which setup_env file you want, and source (or dot) that file directly at the prompt of your current interactive shell.

Presumably, you can write a shell script that lists a set of choices, accepts input from the keyboard, and sources the chosen file. If the user sources this shell script, and answers the prompt correctly, the intended environment settings will take effect in the current interactive shell:

$ cat s1.sh
export FOO=BAR

$ cat s2.sh
export FOO=BAZ

$ cat test.sh
ls s?.sh
echo -n which one :
read j
source $j

$ source test.sh
s1.sh  s2.sh
which one :s1.sh

$ echo $FOO
BAR

$ source test.sh
s1.sh  s2.sh
which one :s2.sh

# echo $FOO
BAZ
[download]

Sorry, but I don't see any other way to do it (shell just ain't like perl).

ANOTHER update: I take that back. There is a way to do it. See another reply of mine, further down in this thread.