#!/usr/bin/perl
my $file = '/output.txt';
open DATA, "$file" or die "can't open file";
my @array = <DATA>;
  for($i=1; $i < 10; $i++) {
    foreach my $found ($array[$i]) {
      if ( $found =~ /string1/ ) {
        my @new = join($array[$i], $array[$i++]);
      }
    }
  }
close (DATA);