For strict, I'd show them a simple example of mistyping a variable name and provide the two ways to "fix" the error: 1) correct the spelling of the variable name, 2) comment out use strict.
Of course, if their program is just missing the 'my' (and doesn't contain other bugs), 1) doesn't apply, and 2) shuts off the error messages, and generates the correct output.

In reply to Re^2: On Commenting Out 'use strict;' (errors) by Anonymous Monk
in thread On Commenting Out 'use strict;' by Old_Gray_Bear

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