sub straight_merge {
	my ($array)=(@_);
	my $buffer=[];
	$#$buffer=$#$array;
	my $len=1; # starts with "runs" of length 1
	while ($len<@$array) {
		my ($al,$ar)=(0,$#$array);
		my ($bl,$br)=(-1,scalar @$array);
		my $dir=1;
		my ($lremain,$rremain)=($len,$len); # how many elements from each side
		PASS:
		while ($al<=$ar) {
			if ($array->[$al] < $array->[$ar]) {
				$bl+=$dir;
				$buffer->[$bl]=$array->[$al];
				$al++;
				next if --$lremain>0;
				while (1) {
					$bl+=$dir;
					last PASS if $bl==$br;
					$buffer->[$bl]=$array->[$ar];
					$ar--;
					last unless --$rremain;
				}
			} else {
				$bl+=$dir;
				$buffer->[$bl]=$array->[$ar];
				$ar--;
				$rremain--;
				next if $rremain>0;
				while (1) {
					$bl+=$dir;
					last PASS if $bl==$br;
					$buffer->[$bl]=$array->[$al];
					$al++;
					last unless --$lremain;
				}
			}
			#Switch sides
			($lremain,$rremain)=($len,$len);
			$dir=-$dir;
			($bl,$br)=($br,$bl);
			if ($ar-$al<$len) {
				# do a partial copy
				while (1) {
					$bl+=$dir;
					last PASS if $bl==$br;
					$buffer->[$bl]=$array->[$al];
					$al++;
				}
			}
			#eof PASS
		}
		#flip the buffers
		$len+=$len;
		last if $len>@$array;
		($array,$buffer)=($buffer,$array);
	}
	unless ($array==$_[0]) {
		#do a copy
		@$array=@$buffer;
	}
}