#!/usr/bin/perl

# https://perlmonks.org/?node_id=1228906

use strict;
use warnings;

@ARGV or @ARGV = qw( tst1 tst2 ); # FIXME for testing only
@ARGV == 2 or die "usage: $0 filename1 filename2\n";

my %lines;

for my $file ( @ARGV )
  {
  my $segment;
  open my $fh, '<', $file or die "$! opening $file";
  while( <$fh> )
    {
    if( /^\w/ )
      {
      $segment = $_;
      }
    elsif( $segment && /\w/ )
      {
      $lines{"$segment$_" } .= "\t$file";
      }
    }
  close $fh;
  }
my $segment;
for( sort grep $lines{$_} =~ tr/\t// == 1, keys %lines )
  {
  if( $segment && /^\Q$segment\E(.+)/ )
    {
    print "$1$lines{$_}\n";
    }
  elsif( /^(.*\n)/ )
    {
    $segment = $1;
    print s/(?=\n$)/$lines{$_}/r;
    }
  }

[download]

Outputs: 

lodv
     EJHFG      tst1
sdmd
     IJFH       tst2
     LAKJSK     tst2

[download]

In reply to Re: Need to have perl script to compare two txt files and print difference along with under which segment the difference is by tybalt89
in thread Need to have perl script to compare two txt files and print difference along with under which segment the difference is by User_04271983

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