#!/usr/bin/perl -w

use strict;
use Data::Dumper qw(Dumper); 


my @list_of_files =  qw(file1.txt file2.txt);
my %data;
my $file_num = 0;
my $Distance;


foreach my $file_name (@list_of_files) {
    $file_num++;
    my $file = 'File'.$file_num;
    my $flag = 0;

    open FH, $file_name or die "Cannot open $file_name. $!";
    while(<FH>){
        chomp;
        if($_ =~ /\s*(\d+)\s*(\d+\.\d+)/){
		    $Distance=$1;
			 $data{$Distance}{$file}{'Fuel_Consumption'}=$2;
            next;
        }
       }
    close FH;
}

  print Dumper(\%data); 

  my ($tmpDist,$tmpFile,$tempValue);
  print "Merged output\n";
  
 foreach $tmpDist (sort{ $a <=> $b } keys( %data ) ) 
 {
    print "$tmpDist";
    foreach $tmpFile (sort{ lc($a) cmp lc($b) } keys( %{$data{$tmpDist}} ) )
     {
	  $tempValue=$data{$tmpDist}{$tmpFile}{'Fuel_Consumption'};
       print "\t $tempValue";
	 }
    print "\n";
 }