It would be nice if the action/expression language allowed use of a built-in or $macro that would expand to a string literal that describes the context of the execution site of the injected action. These macros could be expanded at injection time rather than at run time, eschewing unwinding. With them, a rule pair vaguely like this could enable lightweight callgraph tracing:

RULE foo_entry
CLASS ^foo
METHOD bar()
AT ENTRY
DO SOME_PRINT_THING($class, $method, "entered")
ENDRULE

RULE foo_exit
CLASS ^foo
METHOD bar()
AT EXIT
DO SOME_PRINT_THING($class, $method, "exited")
ENDRULE

(Maybe a textualized $macro of the AT <event> field could further compact things.)