#!/usr/local/bin/perl
use strict;
use warnings;


my $data = 'Sending 104 bytes ***
POST /path HTTP/1.0^M
Content-type: text/xml^M
Content-length: 37^M
^M
SENT 104 HEADER
HTTP/1.1 401 Unauthorised^M
Connection: Close^M
Content-Length: 0^M
^M
<?xml version="1.0" encoding="UTF-8"?>
<?path?>
';

#(Update) more like the output you requested
print "Last Value=> ";
while(){
        (my $text = ($data=~ /(<\?.*\?>)/gi))? print qq('$1'\n) : exit;
        }

#OUTPUT:
#Last Value=> '<?xml version="1.0" encoding="UTF-8"?>'
#'<?path?>'