The short answer is no - SPL is not a procedural language
The perhaps more helpful answer is, it depends on what you are trying to achieve. The thing to remember is that SPL processes a pipeline of events, each command in the pipeline processes the events and passes the results onto the next command in the pipeline.
Using rex to match against the values in the field can help you do conditional processing e.g. if the field contains "command sent", as in your second example, you could extract the endpoint (you may have to adjust this depending on what your events actually look like)
| rex field=msg "Security Agent uninstallation command sent.*,\s+\w+:\s+(?P<endpoint>.+)"Events which don't have a msg field which matches the anchor string will not have the endpoint field added to them, but all the events are passed on to the next command in the pipeline.
Hopefully, that makes sense?
