It isn't cmd.exe you need to prevent from being terminated, but perl.exe that is running your script. The reason your script dies when the user closes the console window, is because perl.exe is being run as a child of cmd.exe which created that console and when you kill a process with children, they die also.

There are various things you can do to address that. Which is applicable depends upon whether the program you are trying to prevent from being killed needs to be able to communicate with the user, and if it does, is it a console app, or a gui app of some form.

But ultimately, why are you trying to stop the user from stopping this program from running?

If it is some corporate policy that dictates this for users of it's corporate network, then whilst I think it is a wrong policy, there are ways that administrators can define policies that will prevent non-administrative users from terminating programs started by administrators. And most large corporations, which is where this kind of big-brother think is prevelant, will have people who know how to do this, or the support contacts through which they can find out.

For any other purpose, particularly if it is of the type "my program is obviously more important than anything else the user might be running", then you should probably think again anyway.