{value: ok, input: (1: 0) 'hello'}
{value: ok, input: (1: 0) 'hello'}
{value: (1: 0) 'world!', input: (1: 0) 'world!'}
{value: (1: 0) 'world!', input: (1: 0) 'world!'}
{value: (1: 0) 'hello', input: (1: 0) 'hello'}
{value: (1: 0) 'hello', input: (1: 0) 'hello'}
{fail: fail, input: (1: 0) 'hello'}
{value: ok, input: (1: 0) 'hello'}
{fail: fail, input: (1: 0) 'hello'}
{value: ok, input: (1: 0) 'hello'}