Matching an exact string is also a valid regex, and I think the GP's simple attempt to use the substitution syntax illustrates JWZ's point even better than a more complex expression. There are so many ways of screwing it up that even a simple joke contained a bug.

The notation s/<regex1>/<regex2> is perl for "replace every instance matching regex1 by regex2. Literal strings are regexes that match only themselves.

But then you still have “getting”