#!/usr/bin/perl
use warnings;
use strict;
my $header =
    join("\\s*\\n",
        'My\s+Header',
        'Page\s+\d+',
        );
$/ = '';
my $file = <DATA>;
while ($file =~/($header\n+)/g)
{
    print "pos = ", pos($file),"\n";
    print $1,"\n";
}

__DATA__
My Header
Page 53
Some Text
Some More Text
Some More Text
Some More Text

My Header
Page 54
3 Chapter Title
My Header
Page 55
Some Text
Some More Text
Some More Text
Some More Text

##</code><code>##

pos = 18
My Header
Page 53

##</code><code>##

#!/usr/bin/perl
use warnings;
use strict;
my $header =
    join("\\s*\\n",
        'My\s+Header',
        'Page\s+\d+',
        );
$/ = '';
my $file = <DATA>;
while ($file =~/($header\n+)/g)
{
    print "pos = ", pos($file),"\n";
    print $1,"\n";
}

__DATA__
My Header
Page 53
Some Text
Some More Text
Some More Text
Some More Text
x
My Header
Page 54
3 Chapter Title
My Header
Page 55
Some Text
Some More Text
Some More Text
Some More Text

##</code><code>##

pos = 18
My Header
Page 53

pos = 93
My Header
Page 54

pos = 127
My Header
Page 55