I have the following rule in prelude-lml:

regex=message received; \
        add_context=MESSAGE_RECEIVED; \
        silent; \
        last;

regex=IP = (\S+); \
        require_context=MESSAGE_RECEIVED; \
        source(0).node.address(>>).address = $1; \
        last;

Now I add the following message to the log file I'm monitoring:

message received
IP = 1.2.3.4

This results in a segfault of prelude-lml:

- /tmp/test.log: Metadata available, starting log analyzis at offset 18341.
prelude-lml.c:lml_dispatch_log:225: [LOG] message received
could not match prefix against log entry: message received.
pcre-mod.c:pcre_context_new:998: [MESSAGE_RECEIVED]: creating context (expire=60s).
prelude-lml.c:lml_dispatch_log:225: [LOG] IP = 1.2.3.4
could not match prefix against log entry: IP = 1.2.3.4.
Segmentation fault

The rule works as expected when I change source(0).node.address(>>).address to
source(>>).node.address(>>).address.

My version:

[root@blah ~]# prelude-lml --version
prelude-lml-0.9.9