use warnings;
use strict;

use Data::Dumper;
local $SIG{__WARN__} = sub { warn "outer: $_[0]" };
warn "one\n";
{
	local $SIG{__WARN__} = sub { warn "inner 1: $_[0]" };
	warn "two\n";
	{
		local %SIG;
		warn "three\n";
		print Dumper(\%SIG);
		{
			local $SIG{__WARN__} = sub { warn "inner 2: $_[0]" };
			warn "four\n";
		}
	}
	warn "five\n";
}
warn "six\n";

__END__

outer: one
inner 1: two
inner 1: three
$VAR1 = {};
inner 2: four
five
outer: six