If it's going to be read, it will have to be unavoidable.

I'd say that to make it efficient, there has to be JavaScript executed when the users submits the form. This JS will have to check the textarea field and look for the words use strict;. This can be done using the JS version of regexes. (Yes, they exist, for those of you that didn't believe so. Not as powerful as Perl regexes, but they do exist.)
If the use strict; is missing in the textarea, then a JS confirm() with an appropriate message shall be shown to the user, including the option to submit anyway or to cancel the submission.

Then it would at least stand a chance to be read.

Now, with the general (lack of) appreciation for JS at the Monastery, this may not be an option. But there's a (the?) solution.

The white hole.

P.S. <OPINION> JavaScript does have it's uses.</OPINION>