use strict;
use warnings;

open my $inFH, q{<}, \ <<EOD or die $!;
XXXXX - additional test 1
XXXXX - additional test 1
ZZZZZ
HHHHH - additional test 1 output expected
PPPPP
XXXXX is my name 1
XXXXX is my name 2
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
GGGGG
XXXXX - additional test 5
XXXXX - additional test 5
EOD

my @buffer;
while ( not eof $inFH )
{
    push @buffer, scalar <$inFH>;
    if ( $buffer[ -1 ] =~ m{XXXXX} )
    {
        last if eof $inFH;
        push @buffer, scalar <$inFH>;
        push @buffer, scalar <$inFH>
           while $buffer[ -1 ] =~ m{XXXXX} and not eof $inFH;
        @buffer = ();
    }
    else
    {
        print shift @buffer
           unless scalar @buffer == 1 and not eof $inFH;
    }
}

close $inFH or die $!;

##</code><code>##

HHHHH - additional test 1 output expected
KKKKK
UUUUU
BBBBB
NNNNN
RRRRR - additional test 4