#!/usr/bin/perl

use strict;
use warnings;

use Data::Dumper;

#  change line delimter
$/ = "END";

while (<DATA>) {

    my $line = $_;

    #  match REGEX across multiple lines
    $line =~ /START(.*)END/s;

    #  get the match
    my $contents = $1;

    print Dumper $contents if defined $contents;;

}


__DATA__
XXXX

YYYY

START

These are the first

set of lines

which are to be extracted

END

XXX

ZZZ

YYY

START

These are the second

set of lines

which are to be extracted

END

aasds

tteret

tertetr