use strict;
use warnings;

my $kPreLines = 1;
my $kPostLines = 1;
my $skipping;
my @bufferedLines;

while (defined (my $line = <DATA>) || @bufferedLines) {
    push @bufferedLines, $line if defined $line;
    
    while (@bufferedLines && $skipping) {
        shift @bufferedLines;
        --$skipping;
    }
    
    print shift @bufferedLines while @bufferedLines > $kPreLines + 1;
    next if !@bufferedLines;
    
    if ($bufferedLines[-1] =~ /XXXXX/) {
        $skipping = $kPostLines;
        @bufferedLines = ();
        next;
    }
    
    next if defined $line;
    
    print @bufferedLines;
    last;
}


__DATA__
QQQQQ
PPPPP
XXXXX is my name
YYYYY
KKKKK
UUUUU
BBBBB
CCCCCC
XXXXX is what I play
KKKKK
NNNNN