Well, I feel bit ithcyitchy, so here's a one (probably generic) way to do it.

use strict;
use warnings;

my @source = qw(Sun Moon Pluto Venus Neptune);
my @target = @ARGV ? @ARGV : qw(Sun Moon);

print is_target_in_source(\@target, \@source), "\n";

sub is_target_in_source {
    my($target, $source) = @_; # omits arg validation
    my %target = map { $_ => 1 } @$target;
    my $in = 0;
    $target{$_} && $in++ for @$source;

    return $in == @$target ? 'Yes' : 'No';
}
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One can also play with one or more functions in List::MoreUtils.

But I found Array::Utils simpler to use:

use strict;
use warnings;
use Array::Utils 'intersect';

my @source = qw(Sun Moon Pluto Venus Neptune);
my @target = @ARGV ? @ARGV : qw(Sun Moon);
my @in = intersect @target, @source;
print @in == @target ? 'Yes' : 'No';
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Update: See also this FAQ entry