Sadly File::ReadBackwards doesn't provide the ability to specify encodings or PerlIO layers. It just reads the file as bytes. (File a bug report!)

That doesn't mean your task is impossible - you just need to manually encode/decode in a few places.

use 5.008;
use strict;
use warnings;

use Encode qw( encode decode );
use File::Temp qw( tempfile );
use File::ReadBackwards qw();

# Pick a random filename
(undef, my $filename) = tempfile();

# Create some content for an example
{
    open my $fh, ">:encoding(UTF-32LE)", $filename
        or die "can haz file?? $!";
    print $fh "$_\n" for qw/ foo bar baz /;
    close $fh;
}

# Now let's open it. Note that we need to tell File::ReadBackwards
# that the line seperator is the UTF-32-encoded version of "\n".
my $fh = "File::ReadBackwards"->new(
    $filename,
    encode("UTF-32LE", "\n") => 0,
) or die "can haz file?? $!";

# Read each line
while (defined(my $line = $fh->readline))
{
    # Need to decode line from UTF-32 to Perl's internal encoding
    $line = decode("UTF-32LE", $line);
    
    print "GOT: $line";
}

# Delete our temp file
unlink $filename;
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