#!/usr/local/bin/perl -w
use strict;

my $data = do { local($/); <> };

print qq{$1\n} if ( $data =~ /(Testnok =[^>]+>)/s )

##</code><code>##

perl -e 'print $1 if ( do{local $/; <>} =~ /(Testnok =[^>]+>)/s)' data.txt