#!/usr/bin/perl
use strict;
use warnings;
use Text::Diff;
use Data::Dumper;

my @output;

my $diff = diff ("test.txt","test2.txt", { OUTPUT => sub {
    my $item = shift;
    for(split(/\n/,$item))
    {
      push(@output, $_) if(m!^[+-]/!);
    }
  }});

print Dumper($diff,\@output);