1   3    5
2   7    6
3   10   7

##</code><code>##

1   3   5
2   4   6
3   3   4

##</code><code>##

#!/usr/bin/perl
use strict;
use warnings;

my $prev_2 = 0;

while (<DATA>) {
    my ($c1, $c2, $c3) = split;
    printf "%3d %3d %3d\n",
            $c1, $c2-$prev_2, $c3;
    $prev_2 = $c2;
}

__DATA__
1   3    5
2   7    6
3   10   7

##</code><code>##

  1   3   5
  2   4   6
  3   3   7