However, you may find that once you have CGI::Ajax installed, there may be additional dependencies that are also required.

Note that all modules that are XS based will have to be recompiled to work against a new version of perl (if I'm not mistaken), so just having them in place will likely not be enough to prevent breakage.

OP should have a development environment that mirrors the production system in order to ensure a smooth and non-impactful upgrade. It would also be very wise to run under Perlbrew or an otherwise alternate perl instead of using the system perl.