The OP's posted code does not include an assignment to $scandir
It does not, but the OP does mention UTF-8, so $scandir being UTF-8 is a possibility, to say the least.
The OP's posted code does not contain umlauts
It doesn't have to be umlauts, what matters is whether $scandir is UTF-8. Make this change to your code and see what happens: 
use utf8; # just for utf8::upgrade

# bytewise, this is already UTF-8...
my $scandir = './pm_1080490_utf8_readdir';

#... but we need to flag it as such for
# the problem to manifest itself:
utf8::upgrade $scandir;
# now on to readdir

[download]
the OP's posted code does not require use utf8
Right, it does not. And use utf8 is not absolutely necessary in the above test code - use -CS/binmode or -CA to initialize $scandir.
If you're referring to the output from that containing: FLAGS = (PADMY,POK,pPOK,UTF8) Then the UTF8 part of that is caused by the umlaut in 'für'.
Does that code not answer your:
[use utf8] has nothing to do with the:... flagging variables
# under 'use utf8'
    FLAGS = (PADMY,POK,pPOK,UTF8)
    ... "f\303\274r"\0 [UTF8 "f\x{fc}r"]
# no utf8
    FLAGS = (PADMY,POK,pPOK)
    ... "f\303\274r"\0

[download]
Does the first variable have the UTF8 flag or does it not? What about the second variable? Aren't those two strings exactly the same?
I'm out of this thread.

In reply to Re^8: treat files with umlauts (utf) by hazylife
in thread treat files with umlauts (utf) by mike.scharnow

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.