for ($i = 1; $i < 5; $i++){
$a[$i]{'name'} = "file$i";
open IN, "<file$i" or die $!;
while(<IN>){
        if (/(\w)\t(\w)\t([\d\.]+)/){
                $a[$i]{"$1$2"} = $3;
                $a[$i]{'total'} = sprintf('%.2f', $a[$i]{'total'}+=$3);
        }
}
close(IN);
}

foreach $key ('name', grep {$_ ne 'name'} sort keys $a[1]){
        print join "\t", $key, map($_->{$key}, @a[1..4]),"\n";
}

##</code><code>##

name    file1   file2   file3   file4
AB      12.00   01.00   02.00   62.00
CD      13.00   04.00   03.00   43.00
EF      11.00   42.00   15.00   24.00
GH      22.00   34.00   20.00   26.00
total   58.00   81.00   40.00   155.00

##</code><code>##

~@deb:~/perl/9# cat file1
A       B       12.00
C       D       13.00
E       F       11.00
G       H       22.00
~@deb:~/perl/9# cat file2
1       A       B       01.00
2       C       D       04.00
3       E       F       42.00
4       G       H       34.00
~@deb:~/perl/9# cat file3
A       B       02.00
C       D       03.00
E       F       15.00
G       H       20.00
~@deb:~/perl/9# cat file4
1       A       B       62.00
2       C       D       43.00
3       E       F       24.00
4       G       H       26.00