Whenever you mix a non-decoded (binary, i.e. octets) string with a text string (utf8 flag on), Perl will silently upgrade the binary string, assuming it's in ISO-8859-1 encoding. "Mixing" here refers to actions such as comparing (as with eq), regex matches, concatenation, etc.

Thus, even though the strings $x and $y are different here with respect to their internal representation (as can be shown with Devel::Peek::Dump() — e.g. a0 ($x, binary) vs. c2 a0 ($y, utf8) ), this difference does not show up in the comparison result, because the binary string ($x) is implicitly upgraded for the comparison.

Also, the caveat is talking about decode("utf8",...) (not decode("iso-8859-1",...)), so it doesn't really apply here anyway...

In reply to Re^2: question about Encode::decode('iso-8859-1', ...) by almut
in thread question about Encode::decode('iso-8859-1', ...) by perl5ever

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.