perl -nE '/([\r\n]{1,2})/; print(unpack("H*",$1))' in.txt
0d0a

##</code><code>##

use v6;
use experimental :pack;

my $fn = 'in.txt';

my $fh = open $fn, chomp => False; # I've also tried :bin
for $fh.lines -> $line {
    if $line ~~ /(<[\r\n]>**1..2)/ {
        $0.Str.encode('UTF-8').unpack("H*").say;
    }
}

##</code><code>##

/(\n)/
/(\v)/