in reply to There is a way to LOCK a SCALAR?

With 5.8.0, there was added a builtin way to do this: 
Internals::SvREADONLY($your_scalar, 1);

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As the name reflects, it was added for internal use (by the restricted hash feature). Don't depend on it staying there or under that name in future perl releases.

In Section Seekers of Perl Wisdom