#!/usr/bin/perl

use warnings;
use strict;

while (<DATA>) {
    if (m?alpha?) {
        print "+ $_";
    } else {
        print "- $_";
    }
}

__DATA__
beta
beta
alpha
beta
beta
alpha
alpha
beta

##</code><code>##

- beta
- beta
+ alpha
- beta
- beta
- alpha
- alpha
- beta