$SIG{__WARN__} = \&mywarn;
# ...
sub mywarn {
	my $warning = shift;
	my $i = 0;
	open (WRNLOG, ">>Warnings.log") || warn "Can't open warnings log file: $!";
	# If open failed, output will be discarded
	print STDOUT "WARNING: $warning";
	print WRNLOG "WARNING: $warning";
	print STDOUT "         Stack Trace:\n";
	print WRNLOG "         Stack Trace:\n";
	while (caller($i)) {
		my (undef, $filename, $line, $sub) = caller($i);
		print STDOUT "         $filename ($line) --- $sub\n";
		print WRNLOG "         $filename ($line) --- $sub\n";
		$i++;
	}
	print STDOUT "\n";
	print WRNLOG "\n";
}