use strict;
use warnings;

my $flag = 0;
while (<DATA>) {
    if (/XXXX/) {
        $flag = 1;
    }
    elsif ($flag) {
        print;
        $flag = 0;
    }
}

__DATA__
ZZZZZZZZZZZZ
YYYYY
XXXX
XX
XXXX
3333
ii
XXXX
asdfddd