What you are asking about I believe is actually beyond the scope of this on-line community's regular discussion.

However, let me say this about what you are asking about since I have some small experience with what you are talking about.

Perl CGI is not going to have any mechanism built into it for clustering and recovery of "in-flight" transactions. If you lose a cluster node in the middle of the execution of something as transient as CGI code, sorry it is going to be lost.

You can do stuff though to help in recovery of the user experience. What I'm going to suggest is not all inclusive, but will help.

If your scripts have some notion of a "session" and you use some sort of back end persistance storage (shared of course) to store the state of your session along with enough hints at least then your user can hit "refresh" and continue their session. However this is not foolproof and should be implemented carefully with proper session timeouts etc.

You will notice I have not mentioned cookies. These can be used as well for sessioning and providing the CGI with arecovery point. My personal preference is to not use them but to code a SESSION_ID in my HTML code that is feeding the CGI.

Hope this helps.