I am trying to work out how to get a file handle object from IO::File to be opened with specific PerlIO layers, and also specify the opening permissions with POSIX flags.
An example WITHOUT using POSIX flags is

#!/usr/bin/perl -w

use strict;

use IO::File;
use PerlIO;
use Data::Dumper;

my $fname = 'big.txt';

my $fh = IO::File->new($fname, "<:utf8")
  or die "cannot open $fname :: $!";

STDERR->print(Dumper([PerlIO::get_layers($fh)]));

$fh->close();
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Output from this is

$VAR1 = [
          'unix',
          'perlio',
          'utf8'
        ];
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I want to do something like this

#!/usr/bin/perl -w

use strict;

use IO::File;
use PerlIO;
use Data::Dumper;

my $fname = 'big.txt';

my $fh = IO::File->new($fname, O_RDONLY, ":utf8")
  or die "cannot open $fname :: $!";

STDERR->print(Dumper([PerlIO::get_layers($fh)]));

$fh->close();
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and get the same result, but I can't seem to get the syntax right - any clues of how to use POSIX flags and PerlIO layers together ??