use strict;
use warnings;
use Data::Dumper qw();
use Data::Dump::Streamer qw();

my %switch_param;
my $switch_optional;

$switch_optional->{foo} = 'bar';

my @optional;

for (1 .. 3) {
    @optional = (@optional, $switch_optional);
}

$switch_param{"optional"} = [@optional];

Data::Dump::Streamer::Dump \%switch_param;
print "\n\n";
print Data::Dumper::Dumper (\%switch_param);