On the other hand, does it really matter?

It does to me, since I inspect the results of the regex, including @+ to see how many capture groups there were.

$ perl -wMstrict -le '""=~// or die; print for @+'
0
$ perl -wMstrict -le '""=~/(?:)/ or die; ""=~// or die; print for @+'
0
$ perl -wMstrict -le '""=~/()/ or die; ""=~// or die; print for @+'
0
0
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Updated examples.