Logstash input plugin generator to generate dynamic data for elastic search

I was wondering if we could use regular expression to specify the data to be emitted so that the data that gets generated is as much as possible random or different every time - with the constraint that it fits into the specified pattern.

I am referring to this https://www.elastic.co/guide/en/logstash/current/plugins-inputs-generator.html

can we do something like this?

input {
generator {
lines => [
# specify regexp here
# Emit all lines 3 times.
count => 3