use strict;
use warnings;
use Data::Dumper;

my @array = (1,2,3,4);
my @index = (1,3);

&these(Index=>\@index);

&those(Index=>\@index);

sub these {

    my %args = @_;
    my @index = @{$args{Index}} || ();

    my $dump = Dumper($args{Index});
    print "$dump";

    $dump = Dumper(\@index);
    print "$dump";
}
sub those {

    my %args = @_;
    my @index = @{$args{Index}} or ();

    my $dump = Dumper($args{Index});
    print "$dump";

    $dump = Dumper(\@index);
    print "$dump";
}