All conditions must be met.

Field controlled-field-1 must have value Bar and field controlled-field-2 must include FooBar somewhere in its value to display field BarFoo.

{
  and: [condition1, condition2, ...] // (condition1 AND condition2 AND ...)
}
{
  fields: [
    {
      name: 'controlled-field-1',
      component: 'text-field',
    },
    {
      name: 'controlled-field-2',
      component: 'text-field',
    },
    {
      name: 'BarFoo',
      label: 'Foo is Bar!',
      component: 'text-field',
      condition: {
        and: [
          {
            when: 'controlled-field-1',
            is: 'Bar',
          },
          {
            when: 'controlled-field-2',
            pattern: /FooBar/
          }
        ]
      },
    },
  ]
}

As the value you have to use an array of conditions.

Or you can use a shorthand:

{
  fields: [
    {
      name: 'controlled-field-1',
      component: 'text-field',
    },
    {
      name: 'controlled-field-2',
      component: 'text-field',
    },
    {
      name: 'BarFoo',
      label: 'Foo is Bar!',
      component: 'text-field',
      condition: [{
        when: 'controlled-field-1',
        is: 'Bar',
      }, {
        when: 'controlled-field-2',
        pattern: /FooBar/
      }],
    },
  ]
}