#!/usr/bin/env perl

use strict;
use warnings;

my ($skip, @buf);

while (<DATA>) {
    if ($skip) {
        $skip = 0;
        next;
    } 

    if (/XXXXX/) {
        @buf = ();
        $skip = 1;
    }
    else {
        push @buf, $_;
        $skip = 0;
    }

    if ($. > 1 && @buf >= 2) {
        print for @buf[0 .. $#buf - 1];
        @buf = ($buf[-1]);
    }
}

print for @buf;

__DATA__
XXXXX - additional test 1
PPPPP
XXXXX is my name
YYYYY
KKKKK
UUUUU
BBBBB
CCCCCC
XXXXX is what I play
KKKKK
NNNNN
ZZZZZ - additional test 2b
XXXXX - additional test 2a
QQQQQ - additional test 3
RRRRR - additional test 4