Re: Which signals are unsafe?

[BrentDax]

$SIG{__WARN__} isn't a real signal, so it's safe. I believe that all signals have been safe since 5.8.

Have you looked at the Carp module? It can be used with $SIG{__WARN__} to print backtraces. Perhaps you could do something like this:

use Carp 'cluck';
$SIG{__WARN__}=\&cluck;
open(STDERR, "|tee -a Warnings.log") or die "Can't open STDERR to tee:
+ $!";

It's not exactly the same as what you have; most notably, all STDERR output would go to Warnings.log, not just warnings. Fixing this is left as an exercise for the reader. ;^)

If nothing else, Carp's longmess sub can handle the backtracing for you.