If you want to temporarily change the PerlIO layers of a handle, your best bet might be to dup the handle. 
use strict;
use warnings;

use PerlIO qw( );

sub dump_layers($*) {
    my ($prefix, $fh) = @_;
    my @layers = PerlIO::get_layers($fh);
    print($prefix, join(', ', @layers), "\n");
}

dump_layers('before: ', STDERR);

{
   open my $fh, '>&', STDERR or die $!;  # Dup the handle
   binmode $fh, ':encoding(UTF-8)';      # Do anything to the dup.
   dump_layers('local:  ', $fh);
}

dump_layers('after:  ', STDERR);         # The original is unaffected.

[download]
before: unix, perlio
local:  unix, perlio, encoding(utf-8-strict), utf8
after:  unix, perlio

[download]

The package variable itself could be replaced with the dup for the duration of the inner scope, but it shouldn't normally be needed.

In reply to Mini-Tutorial: Scoped changes to PerlIO layers by ikegami

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.