The `qr//` was a convenient way to unify multiple `@ARGV` elements, but it was also a potential performance optimization for any more complicated regular expressions.  Perl would be sure to only compile the regex once per highlight invocation, rather than once per input line.  I'm not enough of an expert on perl's interpreter to know if it would be able to cache the compiled pattern anyway, so the `qr//` approach seemed safer to me.

With that said, I've never written a benchmark for this (the tool doesn't even have regression tests!), so there may be no effective performance difference.