use Unicode::String qw/utf8/;

    my $name = "трудная строка";
    my $u=utf8($name);

    # ready; use it at your will:
    my $s = $u->hex;
    $s=~s/U\+00(\w\w)/my($r,$p)=((pack 'H*',$1),$&);if($r=~m(^[\w ]$)){$r}else{$p}/eg;