add LAYER option to specify file binmode [rt.cpan.org #37598]

[xdg]

https://rt.cpan.org/Ticket/Display.html?id=37598

How about having a LAYER option, so uses could specify, e.g. LAYER=>':utf8' or other IO 
disciplines/layers?

[martinvonwittich]

In a similar vein, would it be possible for File::Temp to automatically enable the UTF8 layer when Perl is running with -CSDAL?

I had expected this code to write valid UTF-8:

#!/usr/bin/perl -CSDAL
use warnings;
use strict;
use utf8;
use File::Temp;

my ($fh, $fn) = File::Temp::tempfile("foo.XXXXXXXX", DIR => "/tmp");
#binmode($fh, ":encoding(UTF-8)");
printf "%s\n", $fn;
print $fh "üäü\n";
close $fh;

but currently the binmode is needed to get valid UTF-8 output.