for my $file (@files) {
	my $ok = open (my $fh, "<", "$dir/$file.txt");
	if (not $ok) {
		warn "Couldn't open file '$dir/$file.txt' ($!)\n";
		next;
	}
	while (my $line = <$fh> ) {	
		chomp $line;
		my @fields = split("\t",$line);
		my $key = $hash{"$fields[0].$fields[1]"} or next;
		$result{$key}{$file} += $fields[3];
	}
	close $fh;
}

my $hline = join("\t",@files);
print qq|\t$hline\n|;
for my $key ( sort keys %result ) {
	my $amt = $result{$key};
	my @cols = map { $amt->{$_} ? sprintf("%.1f",$amt->{$_}) : 'n/a' } @files;
	my $line = join("\t",@cols);
	print qq|$key\t$line\n|;
}