I think a regular expression is a bit overkill for the situation. You could probably do it much faster using unpack:

my ($year,$month,$day) = unpack 'a4 x1 a2 a2', $date_cfg;
my $new_date = "$month/$day/$year";
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or if you want to do it in one line:

my $new_date = join '',(unpack 'a4 x1 a2 a2',$date_cfg)[1,2,0];
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