func multisplit(sep, str, keep_sep=false) {
    sep = sep.map{.escape}.join('|');
    var re = Regex.new(keep_sep ? "(#{sep})" : sep);
    str.split(re, -1);
}

[false, true].each { |bool|
    say multisplit(%w(== != =), 'a!===b=!=c', keep_sep: bool);
}