Let's create a text-based imposter with multiple stubs. Binary imposters cannot use the matches predicate.

POST /imposters HTTP/1.1
Host: localhost:<%= port %>
Accept: application/json
Content-Type: application/json

{
  "port": 4550,
  "protocol": "tcp",
  "mode": "text",
  "stubs": [
    {
      "responses": [{ "is": { "data": "first response" } }],
      "predicates": [{
        "matches": { "data": "^first\\Wsecond" },
        "caseSensitive": true
      }]
    },
    {
      "responses": [{ "is": { "data": "second response" } }],
      "predicates": [{ "matches": { "data": "second\\s+request" } }]
    },
    {
      "responses": [{ "is": { "data": "third response" } }],
      "predicates": [{ "matches": { "data": "second\\s+request" } }]
    }
  ]
}

The first stub requires a case-sensitive match on a string starting with "first", followed by a non-word character, followed by "second":

echo 'first second' | nc localhost 4550

first response

The second stub is not case-sensitive.

echo 'Second Request' | nc localhost 4550

second response

The third stub will never run, since it matches the same requests as the second stub. mountebank always chooses the first stub that matches based on the order you add them to the stubs array when creating the imposter.