use strict;
use warnings;

my $flag = 0;
while (<DATA>) {
    print if $flag;
    if ($flag and /XXXX/) {
        eval('$demons->fly_out($nose)');
    }
    $flag = /XXXX/;
}

__DATA__
ZZZZZZZZZZZZ
YYYYY
XXXX
XX
XXXX
3333
ii
XXXX
asdfddd