This because the values in the perl string are multi-bytes characters.

No, the values in the string are bytes 0x80 and 0x81 for all the cases. 

$_ = 12;        # Value is 12, the number of months in a year.
print "$_\n";   # Value is still 12, the number of months in a year,
                #    just stored differently.

[download]
$_ = "\x80\x81";    # Value is bytes 80 81
utf8::upgrade($_);  # Value is still bytes 80 81,
                    #    just stored differently.
print(length($_), "\n");  # 2

[download]

And all it took was 57 levels of exchanges for you to get around to admitting it.

Admit what? That some strings of bytes can be stored using multiple bytes? That was my point from the very beginning.

In reply to Re^57: Interleaving bytes in a string quickly by ikegami
in thread Interleaving bytes in a string quickly by BrowserUk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.