The above is incorrect, as it "decodes" the torrent file too. You want binary mode (:raw) for that, and an encoding layer (:encoding(UTF-8)) on the output.

Unfortunately, while we can set a default encoding layer for the files read via ARGV, there's no way to make it use binary mode. It gives us a mess.

perl -e'
   use v5.36;
   use utf8::all;
   use Bencode qw( bdecode );
   use File::Slurper qw( read_binary );
   binmode STDIN;

   sub process_torrent {
      say bdecode( $_[0] )->{info}{name};
   }

   if ( @ARGV ) {
      process_torrent( read_binary( $_ ) ) for @ARGV;
   } else {
      process_torrent( do { local $/; <STDIN> } );
   }
'
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Outside of Windows, you can probably get away with not using binary mode.

perl -gne'
   use v5.36;
   use Bencode qw( bdecode );
   binmode STDOUT, ":encoding( UTF-8 )";
   binmode STDERR, ":encoding( UTF-8 )";
   say bdecode( $_ )->{info}{name};
'
[download]