Oh huh, TIL in Ruby `^` *always* means "start of line", whereas in many
languages' regular expression engines it means "start of string" unless
you enable a special multiline flag for the pattern.
I've fixed this in a number of expressions now!
I'm noticing this in the context of doing some security training work
where this the cause of a sample vulnerability, but, looking at our own
case, I don't think there was anything *abusable* here? But this is
just more correct, so let's be more correct!