If there are many files that will not have a match, this might actually be faster, because you will save on IO writes. The perl -i will always write to a new (temporary) file, even if it turns out the content is the same - after all, Perl can't know there isn't a match. So, you will do more IO writes, and your OS goes twice as fast through its buffer cache.

It's hard to say whether a grep is worthwhile. Without knowing more about the content of the files, I won't dismiss it.

Abigail