You really want that reject list as a hash. Consider:

my @do_not_want = qw{ ytd mtd wtd };
my %rejects;

@rejects{@do_not_want} = ();

foreach my $anything_but ( grep {! exists $rejects{$_}} keys %hash ) {
    print $anything_but . "\n";
}
[download]

which in the context of the rest of your sample prints:

Meat_Pie
Jumbo_Tron
Word
[download]

The magic bit is @rejects{@do_not_want} = (); which uses a hash slice (see Slices) to create a hash with an entry for each unique element in @do_not_want.

Update: provided better hash slice link