Those flags are used later to set ruby values in the returned hash. Here the year local variable is converted to a ruby integer and assigned as the value of the year ruby symbol key.
Anyway, I'm sure I covered that too quickly, but you could have a whole conference just about Ragel.
home_run just uses the very basics of Ragel's capabilities, but the use of Ragel enables home_run to parse many times faster than the standard library if you are using a format that the Ragel parser understands, which is currently ISO-8601, RFC 2822, HTTP, and the Apache Common Log Format.