sub split_len {
    ## split_len( $chars, $string[, $limit] ) 
    ## - splits $string into chunks of $chars chars
    ## - limits number of segments returned to $limit, if provided
    my ($chars, $string) = @_;

    my ($i, @result);  
    for ($i = 0; ($i+$chars) < length($string); $i+=$chars) {
        last if (defined $limit && @result >= $limit);
        push @result, substr($string, $i, $chars);
    }

    # deal with any short remainders
    return @result if (defined $limit && @result >= $limit);
    if ($i > length($string)-$chars) {
        push @result, substr($string, $i);
    }

    return @result;
}