use strict;
use warnings;
my $previous="";
while(<DATA>){
    if(/XXXXX/){
        <DATA>;
        $previous="";
    }else{
        print $previous;
        $previous=$_;
    }
}
print $previous;
__DATA__
PPPPP
XXXXX is my name
YYYYY
KKKKK
UUUUU
BBBBB
CCCCCC
XXXXX is what I play
KKKKK
NNNNN