use strict;
use warnings;

open(my $fh, '>:unix', "test.txt") or die "test.txt: $!";
foreach my $i (1..20) {
    print $fh "iteration $i\n";
    sleep(5);
}
close($fh);

##</code><code>##

use strict;
use warnings;
use PerlIO;

print join(', ', PerlIO::get_layers(*STDOUT)) . "\n";
binmode(*STDOUT, ":pop");
print join(', ', PerlIO::get_layers(*STDOUT)) . "\n";
__END__
unix, perlio
unix