The (most likely) short answer is that your new installation is lacking a non standard module. Check for use statements and install missing modules with your package manager if you rely on system perl.

Re: os upgrade breaks cgi is the better long answer.

Normally the error logs of your webserver should already include those messages.

Many CGIs can also meaningfully be started from the command line to see if they even compile. Compare the two installations for differences.

Of course, like already stated by hv we need to know "what it broke means" to avoid more guess work.