Your code only matches one uppercase letter. /[A-Z]+/ will match one or more.
However, now that I reread your question, it seems you only care if there is at least one uppercase letter which, as stated by other posters, your code accomplishes.
I don't mind occasionally having to reinvent a wheel; I don't even mind using someone's reinvented wheel occasionally. But it helps a lot if it is symmetric, contains no fewer than ten sides, and has the axle centered. I do tire of trapezoidal wheels with offset axles. --Joseph Newcomer