Now this was a cargo cult anti-pattern to write home about.
Doing painful save-and-restore bookkeeping around a separate
`magic_overruled` decoy global is just as messy as doing painful
save-and-restore logic around `p_magic` itself. only that now you need
to wrap every access to the effective value in a function call.
This replaces this with a marvellous new Clean Code technique™:
passing in the intended behavior as a function parameter to functions
where either the option or an explicit value might be used.
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