Stop proccesing events/lines after first grok match

Elastic Stack Logstash
10 
input { generator { count => 1 lines => [ '
Foo: 21
Another Foo: 14
Final Foo: 734591' ] } }

ruby { code => 'event.set("Foos", event.get("message").scan(/Foo: ([0-9]+)/))' }
output { stdout { codec => rubydebug { metadata => false } } }

will produce

      "Foos" => [
    [0] [
        [0] "21"
    ],
    [1] [
        [0] "14"
    ],
    [2] [
        [0] "734591"
    ]

scan finds the three occurrences of Foo: followed by a number. For each occurence it returns an array of capture groups (parentheses inside the regexp). In my case there is only one capture group for each occurrence.