It seems your perl has been already upgraded. If you want to stick with your older version of perl, if it's still on your computer, then put the full path to the actual executable in the shebang line.

You may want to upgrade all of your modules instead, especially the binary ones, since they won't be compatible with the new perl executable any more. Then I'm sure I've seen ways to do so by means of suitable modules; only, I'm not sure which ones, but chances are that they may be Bundle::CPAN or CPANPLUS.