How do I read UTF-8 with diamond operator (<>)?

Question

I want to read UTF-8 input in Perl, no matter if it comes from the standard input or from a file, using the diamond operator: while(<>){...}.

So m

Answer 1

Try to use the pragma open instead:

use strict;
use warnings;
use open qw(:std :utf8);

while(<>){
    my @chars = split //, $_;
    print "$_" foreach(@chars);
}

You need to do this because the <> operator is magical. As you know it will read from STDIN or from the files in @ARGV. Reading from STDIN causes no problem as STDIN is already open thus binmode works well on it. The problem is when reading from the files in @ARGV, when your script starts and calls binmode the files are not open. This causes STDIN to be set to UTF-8, but this IO channel is not used when @ARGV has files. In this case the <> operator opens a new file handle for each file in @ARGV. Each file handle gets reset and loses it's UTF-8 attribute. By using the pragma open you force each new STDIN to be in UTF-8.