How can I walk through two files simultaneously in Perl?

Question

I have two text files that contain columnar data of the variety position-value, sorted by position.

Here is an example of the

Answer 1

Here is a quick solution. If the data in both files is pretty much equivalent (e.g. same number of lines), you don't really need to store in hash tables. But I thought it would be helpful in case you the data is scrambled.

Code:

open(f1, ") and ($line2 = )){
     chomp($line1);
     chomp($line2);
     # split fields 1 and 2 into an array
     @LINE1 = split(/\t/, $line1);
     @LINE2 = split(/\t/, $line2);
     # store data into hashes
     $data1{$LINE1[0]} = $LINE1[1];
     $data2{$LINE2[0]} = $LINE2[1];
     # compare column 2
     if ($data1{$LINE2[0]} == $data2{$LINE1[0]}){
           # compute something
           $new_val = $data1{$LINE2[0]} + $data2{$LINE1[0]};
           print $LINE1[0] . "\t" . $new_val . "\n";
     } else {
           print $LINE1[0] . "\t" . $data1{$LINE1[0]} . "\n";
     }
}

I hope it helps and let me know if its useful.