See the open pragma. From the synopsis:

# with :std, also affect global standard handles

Here's what I get when I add :std:

perl -e '
use warnings;
use strict;
use utf8;

my $veiði     = "exciting";
my $efnisskrá = "repertoir";

use open IO => qw{:utf8 :std};
print "in my $efnisskrá (efnisskrá) I like to go fishing ($veiði)\n";
'
in my repertoir (efnisskrá) I like to go fishing (exciting)
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