As for caveats with regard to threading

It's a normal Perl scalar. It will get cloned on thread creation like every other. Each thread will be accessing its own copy of it. No problem.

Update: s/a different/its own/

In reply to Re^2: XS: exposing C++ library constant as package variable by ikegami
in thread XS: exposing C++ library constant as package variable by wisnij

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