in reply to Re^2: 'grouping' substrings?
in thread 'grouping' substrings?

That's not exactly true. $& is only inefficient if you have another regexp in your program which doesn't capture.

However, it's use is discouraged, since captures can perform the same task without the "effect at a distance" of $&.

In this case, just replace $& with $1, and you're set.