Your PATH should be pointing at the directory, not the binary, and if you want your system to find that perl first, it should come first in the path. So e.g. PATH="/opt/perl-version/bin:$PATH"

Your shebang line is fine. You could also use "#!/usr/bin/env perl" to get the perl that comes first in your PATH.

You can use the regular CPAN to install modules. Check with "which cpan" that you're calling the right version, or call it explicitly via "/opt/perl-version/bin/cpan".