#! perl -slw
use strict;

my $re_notes = qr[<notes>.*?</notes>];
my $buffer = '';
while (sysread( DATA, $buffer, 2, length $buffer)) {
	$buffer =~ tr[\n][]d;
#	print $buffer;
    while($buffer =~ m[($re_notes)]og ) {
        print $1;
    }
    $buffer = substr($buffer, 1+rindex($buffer, '</notes>'));
}

__DATA__
Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage and irrelevent crap Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage and <notes>This is
 the text I
 am looking
 for split across
 several lines</notes>irrelevent crap
Loads'a junk a garbage and irrelevent crap Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage<notes>This is the text I am looking for on one line embedded</notes> and irrelevent crap
Loads'a junk a garbage and irrelevent crap Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage and irrelevent crap Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage and irrelevent crap Loads'a junk a garbage and irrelevent crap
<notes>This is the text I am looking for on one line on its own</notes>
Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage and irrelevent crap Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage and irrelevent crap
<notes>This is the text I am looking for split
 across two lines</notes> Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage and irrelevent crap Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage and irrelevent crap
Loads'a junk a garbage and irrelevent crap Loads'a junk a garbage and irrelevent crap