You're guessing right. In Perl there is (usually) no data in common between multiple executing copies of a script. If you need to share one or more vars between different copies of a script you have to do that explicitly by mean of shared memory or other IPC methods.

But I'm really really sure I understand what you mean with "class data". My best guess is that you mean a global var defined in the package containing the class and then yes, AFAIK any method of any object derived from that class has access to the global var which is unique for the entire script (but not unique across several executions of it)