Apparently, the $maxNetworkDelay was being triggered when network delays occurs and that actually sends a signal to all threads. This was causing the death of the daemon.

This makes no sense to me at all. I've (briefly) scoured the LWP::UserAgent code, and can see nowhere that it raises a signal. Not as a result of a timeout, nor anything else.

Did I know why I wrote the handler at the top? Partly yes, because I knew all threads were getting the signals in 5.8.4.

Do I know what is happening precisely? Definately not. Would appreciate your views on this

I've recently learned that this (frankly weird) behaviour of signals and threads is different on (at least one variant of) *nix, than it is on Windows. Even with recent versions of both Perl & threads.

As such, whilst I hope my contributions so far have helped you to reaching a solution, I do not feel qualified to comment further on this. Sorry.