Can't upgrade that kind of scalar

Aside from gdb, any fishing tips on how to track this fatal problem down? Can't upgrade that kind of scalar at XXX line NN... Happens intermittently, often on a call to one of these (maybe the first access of $r?): $r-server-server_hostname() $r-connection-remote_ip

Can't upgrade that kind of scalar (and more)

/help which unlock this riddle for me... Cheers, Ed Loehr SYMPTOMS... --- Spurious errors in my error_log with increasingly nasty consequences: Can't upgrade that kind of scalar at XXX line NN... Not a CODE reference at XXX line NN... Modification of a read-only