Thanks for your feedback. Unfortunately adding BREAK to my list of signals still did not cause my code to trigger. The log is still empty after i close the window.

# partially based upon code by BrowserUK from https://www.perlmonks.or
+g/?node_id=629210
use strict;
use Config;
use FindBin;
use File::Spec;

my $log_fn = File::Spec->catfile($FindBin::Bin, "cleanup_handler_log.t
+xt");
my $LOG;

open $LOG, '>>', $log_fn or die "Failed to open log '$log_fn' for appe
+nding ($!)\n";
binmode $LOG;
$LOG->autoflush(1); # disable buffering

my @sigs = split ' ', $Config{ sig_name };
shift @sigs;
print "SIGNALS: @sigs\n";

for ( @sigs ) {
    my $msg = "Signal $_ received\n";
    $SIG{ $_ } = sub{ print $LOG $msg; warn $msg;  };
}

my $count;
while( 1 ) {
    $count += 1 for 1.. 1e6;
    warn $count;
    sleep 3;
}
[download]

SIGNALS: HUP INT QUIT ILL NUM05 NUM06 NUM07 FPE KILL NUM10 SEGV NUM12 
+PIPE ALRM
TERM NUM16 NUM17 NUM18 NUM19 CHLD BREAK ABRT STOP NUM24 CONT CLD
[download]

In that case, the parent process is not signalling your process and it dies when the parent dies. So you need to write a subroutine in C that sets a handler,

BOOL WINAPI SetConsoleCtrlHandler(
  _In_opt_ PHANDLER_ROUTINE HandlerRoutine,
  _In_     BOOL             Add
);
[download]

and another that is called back. The handler routine can then issue a signal of its own for your perl program to trap. It's a bit of a maze but these are the set of functions you can choose from to manage the windows console: https://docs.microsoft.com/en-us/windows/console/console-functions

Update: If you can live with uninterruptable, you could also consider a DOS wrapper that does "START /B wrapper2.bat", where wrapper2.bat runs the perl program. This should then be detached from the console window.

I found some initial attempt to implement SetCtrlHandler in the source of Win32::Console. It is commented out in the C part and in the perl part. So i guess the author of the Module failed to get it running and chose to not implement it. Currently it seems to boil down to either attempting to implement the given Code for SetConsoleCtrlHandler myself, or to decouple my output logic from STDOUT, so i can background the process. Sniff. Would have preferred an easier solution.