I just tried the code and, as one would expect, got the same as lakslunananindia. But if I close FD within the sub handler(), after wrting to it, then it looks like the problem is also solved without fiddling with STDERR so much.

Is there something wrong with closing FD in the signal handler?

I don't have any real experience with signal handlers (though by now I should have had some experience); but coincidentally, I just began exploring them a couple of months ago. I don't get many opportunities to do much exploration, though. So this little node is most instructive for me.

Thanks, all.