PNG.p6

grammar PNG {
    token TOP {
        ^ <header> <chunk> $
    }

    token chunk {
        <length>
    }

    token length {
        . ** 4
    }

    token header {
        . ** 8
        <?{ say $/.Str.encode("latin1"); say $/.Str.encode("latin1") == Buf.new([137, 80, 78, 71, 13, 10, 26, 10]); }>
    }
}

my $str = @*ARGS[0].IO.open(enc => "latin1").read(12);
say "GIVEN =-> ", $str;
say PNG.parse( $str.decode("latin1") );