Actually, looks like utf8::encode is just as dumb as _utf8_off. 
$ perl -MDevel::Peek -MEncode=_utf8_on,_utf8_off,encode -e'
    _utf8_on( my $x = "\200\201" );  # Invalid UTF-8

    utf8::encode( my $utf8 = $x );
    my $enc = encode("UTF-8", $x);
    _utf8_off( my $off = $x );

    Dump $x;
    Dump $utf8;
    Dump $enc;
    Dump $off;
'
  PV = 0x8165280 "\200\201"\0 [UTF8 "\x{1}@"]
  PV = 0x81623f0 "\200\201"\0
  PV = 0x81920f8 "\357\277\275\357\277\275"\0
  PV = 0x81ff040 "\200\201"\0

[download]

Except when the flag isn't on. 

$ perl -MDevel::Peek -MEncode=_utf8_on,_utf8_off,encode -e'
    my $x = "\200\201";

    utf8::encode( my $utf8 = $x );
    my $enc = encode("UTF-8", $x);
    _utf8_off( my $off = $x );

    Dump $x;
    Dump $utf8;
    Dump $enc;
    Dump $off;
'
  PV = 0x8165278 "\200\201"\0
  PV = 0x816b608 "\302\200\302\201"\0
  PV = 0x8195050 "\302\200\302\201"\0
  PV = 0x81ff038 "\200\201"\0

[download]

Your pick.

In reply to Re^5: deal with incorrectly set utf8 flag by ikegami
in thread deal with incorrectly set utf8 flag by Anonymous Monk

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.