#!/usr/bin/perl
use warnings;
use strict;
use feature 'say';


sub encoding {
    my $code = shift;
    open my $STORE_STDOUT, '>&STDOUT' or die $!;
    binmode STDOUT, 'encoding(UTF-8)';
    $code->();
    open STDOUT, '>&', $STORE_STDOUT or die $!;
}


my $utf8 = "\x{3bc}\x{1fc6}\x{3bd}\x{3b9}\x{3bd}";

say 'A:', $utf8;

encoding(sub {
             # Here, no warning is issued.
             say 'B:', $utf8;
         }); # End of scope, STDOUT is no longer affected.

say 'C:', $utf8;