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<register silent="true" event="chat_party|tell_([a-Z])_whatever">input /ma "whatever" (regex)^\1$(/regex)</register>
I'm not even 100% sure that's how you would even work that, I am just tossing that out off the top of my head. Just trying to figure out if you can store a group and back reference it, instead of needing to manually type in characters name.