p6.p6

class IO::String is IO::Handle {
    has Str $.buffer = '';
    has Int $.pos = 0;

    method get(IO::String:D:) {
        return Nil if $!pos >= $.buffer.chars;

        my $start = $!pos;
        my $next-nl = [min] $.nl-in.map({
            $_ => $^nl with $.buffer.index($^nl, $start)
        }).grep(*.key.defined);

        if $next-nl ~~ Num { # if it's Inf, then there's no minimum
            $!pos = $.buffer.chars;
            return $.buffer.substr($start);
        }

        my $chars = 1 + $next-nl.key - $start;
        $!pos += $chars;
        $chars -= $next-nl.value.chars if $.chomp;
        $.buffer.substr($start, $chars);
    }
}

dd IO::String.new(buffer => "hello,\r\nworld!\r\n").get;