Hi,
I think there is a small misunderstanding. Inside the help for Regex host search is written you need to provide a regex which results in exactly one match group.
This is also written inside the official guide.
The following setup is working in my systems without any problem.
Regex host search ($PARAM$.*)
Arguments $1$
The called rule is expecting the complete host name.
PARAM is as you wrote a prefix for all your wanted host names.
Best regards
Andreas