UPDATE: I'd really just be interested in skipping line if it is not UTF-8, or not dealing with these lines at all.

Do you realize that you'd be skipping all four lines you posted since none are valid UTF-8?

It's easy to do:

use strict;
use warnings;

use open ':std', ':locale';

use Encode qw( );

my $log = 'log';

open(my $fh, '<:raw:perlio', $log)
   or die("Can't open log file \"$log\": $!\n");

while (<$fh>) {
    s/\r?\n\z//;
    my $data = (split(/ /, $_, 4))[3];
    my ($text) = eval { decode("UTF-8", $data, Encode::FB_CROAK) }
        or next;
    print($text);
}
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