#!perl

use 5.12.0;
use warnings;

local $/ = "1313";

while (<DATA>) {
    say qq{Found line: $_};
} 

__DATA__
qwerty
qwerty
qwerty
qwerty
qwerty
qwerty

##</code><code>##

$ strange_in_rec_sep.pl
Found line: qwerty
qwerty
qwerty
qwerty
qwerty
qwerty

##</code><code>##

__DATA__
qwerty
qwerty
qwerty
1313
qwerty
qwerty
qwerty

##</code><code>##

$ strange_in_rec_sep.pl
Found line: qwerty
qwerty
qwerty
1313
Found line: 
qwerty
qwerty
qwerty