Log parsing and alerting in kapacitor

Hi all,
I have all my log files coming into influxdb via telegraf (using the “tail” plugin ) . These logs could be of any format . Sometimes they could just be a bunch of print statement , whereas sometimes it could be a standard format like “syslog” or “logcat” .
I’d like to be able to parse these standard log formats and periodically throw an alert if i see say 100 logs which have severity ERROR ( after parsing syslog/logcat ) . I’m guessing kapacitor would be the right place to do this .
However , I feel kapacitor has very few functions which are string related (like grok,regex etc support isnt present) and more towards numbers/math . What would be the best way to solve a problem like this?