Good point, although in this case those variables also don't allow one to differentiate between the last two matches:

$ perl -MData::Dump -e '$a="abc";for(1..6){ $a=~m/.|$/g; dd \@-,\@+ }'
([0], [1])
([1], [2])
([2], [3])
([3], [3])
([3], [3])
([0], [1])
[download]

Update: Hmm, well they can if one adds capture groups, which is kind of the same workaround as I showed here.

$ perl -MData::Dump -e '$a="abc";for(1..6){$a=~m/(.|$)/g; dd \@-,\@+}'
([0, 0], [1, 1])
([1, 1], [2, 2])
([2, 2], [3, 3])
([3, 3], [3, 3])
([3], [3, 3])
([0, 0], [1, 1])
[download]