#!/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()] },
} );