parsimmon: p.or and p.alt wont backtrack

I’ve these two examples which fails

// Input
var input = "hello hello";

//  Parser
var hello = p.string("hello");
var hellos = p.sepBy(hello, p.whitespace);

// Examples
console.info(p.alt(hello, hellos).parse(input));
console.info(hello.or(hellos).parse(input));

// Output
{ status: false,
  index: { offset: 5, line: 1, column: 6 },
  expected: [ 'EOF' ] }
{ status: false,
  index: { offset: 5, line: 1, column: 6 },
  expected: [ 'EOF' ] }

I was expecting both to try the first parser hello and on failure backtrack and continue with hellos. How come this isn’t possible and how would I solve this without having to reimplement the different parsers?

Real world use case: In my application I’ve have created different isolated parsers which initially overlap. Here is some example input (:highlights in vim):

var example1 = "SpellLocal     xxx ctermbg=14 gui=undercurl"
var example2 = "rubyEval       xxx links to Statement"
var example3 = "rubyKeywordAsMethod xxx cleared"

Each line represents a different parser, but happens to look the same in the beginning. Each example have it’s own parser. A line can only be mapped to one parser. I was hoping to do something like below as this would allow me keep the parsers independent.

var input = [example1, example2, example3].sample();
exampleParser1.or(exampleParser2).or(exampleParser3).parse(input)