Class House keeps track that there are 5 houses open.

Are you assuming Perl does this? No language I know does this.

If two process are run of script1, does Class House register 10 House or 5 House???

If the class has code to do this, it depends on that code.

It seems to me that you're asking question based on unfounded assumptions. Classes are package names into which objects are blessed. Period. Everything else is up to you.