Alternative to bytes::length()

[creamygoodness]

Greets,

I have often seen people badmouth the bytes pragma, but there's one thing I use it for: cheaply identifying empty strings with bytes::length()when the strings may be carrying the SVf_UTF8 flag. The length() function can be inefficient for such strings, because it must traverse the entire buffer counting characters:

marvin@smokey:~/perltest $ perl compare_length_efficiency.pl 
        Rate  utf8 bytes
utf8  4.35/s    --  -98%
bytes  185/s 4154%    --
marvin@smokey:~/perltest $

use strict;
use warnings;
use Benchmark qw( cmpthese );

# Make bytes:: functions available, but use character semantics.
use bytes; 
no bytes;

cmpthese(
    100,
    {   bytes => sub { 
            my $smileys = "\x{263a}" x 10_000;
            chop($smileys) while bytes::length($smileys);
        },  
        utf8 => sub { 
            my $smileys = "\x{263a}" x 10_000;
            chop($smileys) while length($smileys);
        },  
    }   
);

Is there an efficient alternative to bytes::length() for this use case elsewhere in core?