Can you please provide an example of the rule expression you tried to apply? Thanks
Here are some examples on how to use string expressions as part of rule condition and action expressions. Note, in the second example
$varA must be an variable you have defined.
$someDeviceId.someAttribute won’t work as device attributes are read-only in this context, i.e. an attribute can only be modified with an action operation defined on the given class.
WHEN subString("$someVar", "A", "g") equals "AA"
THEN toggle denon-avr-power
WHEN denon-avr is present
THEN set $varA := subString("$varB", "A", "g")
"It always takes longer than you expect, even when you take into account Hofstadter's Law.", Hofstadter's Law