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

my @file = ('tst1.txt','tst2.txt');
my %compare = ();

# inputs
for my $n (0..$#file){
  parse_file($n);
}

# output diff
for my $segment (sort keys %compare){
  for my $row (sort keys %{$compare{$segment}}){
    my $rec = $compare{$segment}{$row}; 
    if (defined $rec->[0] && defined $rec->[1]){
      # matched
    } else {
      printf "%s %s\n",$segment,$row;
    }
  }
}


sub parse_file {
  my ($n) = @_;
  my $filename = $file[$n]; 
  my $segment;
  open IN,'<', $filename 
    or die "Could not open $filename : $!";
  while (<IN>){
    s/\s+$//; # trim trailing whitespace
    if (s/^\s+//){
      ++$compare{$segment}{$_}[$n];
    } else {
      $segment = $_;
    }  
  }
  close IN;
}