[ $_, s/^CAORE//r =~ s/(\d+)/sprintf "%06d", $1/ger ] } @aa;

I don't understand the  s/^CAORE//r part of this expression. It seems to be doing nothing, and the sorted output is the same without it:

c:\@Work\Perl\monks>perl -wMstrict -le
"my @aa = qw(
   CORE1 CORE12 CORE8 CORE233 COREA11 COREA12 COREA130 COREA115
   );
 my @sorted = map { $_->[0] } sort { $a->[1] cmp $b->[1] } map {
     [ $_, s/(\d+)/sprintf \"%06d\", $1/ger ] } @aa;
 print qq{@sorted};
"
CORE1 CORE8 CORE12 CORE233 COREA11 COREA12 COREA115 COREA130
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Can you please elaborate?