When you use Apache::DBI or DBI->connect_cached, they both keep a global cache of connections. They will not open a new one unless you use different parameters to open the connection, or the old connection has been disconnected.

I haven't seen that fetchrow_hashref behavior before, but I don't actually use that method. If you don't have RaiseError turned on, definitely do that, since you may be missing errors earlier in the process.