Simpler solution not limited to non-ASCII chars: 

s/(\p{Lu})|\p{Ll}/ defined($1) ? 'U' : 'L' /eg;

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In reply to Re^2: change [A-Z] to U, [a-z] to L with one regex? by ikegami
in thread change [A-Z] to U, [a-z] to L with one regex? by Doctrin

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