I always like learning new things; I wasn't aware of this Getopt::Long feature.

However, I prefer a different way of setting defaults, which mixes well with this:

use Getopt::Long;
my $opt = {
  grot => [qw( a bb ccc )],
};
GetOptions( $opt,
  'grot=s@{2}',
) or die "can't parse options";
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