#!/usr/bin/perl

# http://perlmonks.org/?node_id=1192908

use strict;
use warnings;

use Algorithm::Diff qw(traverse_sequences);

open my $fh1, '<', \<<END;
NAME, ID1, ID2
apple
banana

NAME, ID1, ID3
strawberry
grape

END

open my $fh2, '<', \<<END;
NAME, ID1, ID2
apple
jackfruit

NAME, ID1, ID4
banana
grapes

END

$/ = undef;

my @file1 = <$fh1> =~ /^NAME.*\n(?:(?!NAME).*\n)*/gm;
close $fh1;
my @file2 = <$fh2> =~ /^NAME.*\n(?:(?!NAME).*\n)*/gm;
close $fh2;

#use Data::Dump 'pp'; pp \@file1; pp \@file2;

traverse_sequences(
  [ map /(.*)/, @file1 ], # compare only first lines
  [ map /(.*)/, @file2 ],
  {
  MATCH => sub { print $file1[shift()] },
  DISCARD_A => sub { print $file1[shift()] },
  DISCARD_B => sub { print $file2[pop()] },
  } );
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